v8go

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 Go to latest Published: Feb 3, 2024 License: BSD-3-Clause Imports: 15 Imported by: 0

README

Execute JavaScript from Go

Github release Go Report Card Go Reference CI V8 Build codecov FOSSA Status

V8 Gopher based on original artwork from the amazing Renee French

Usage

import v8 "github.com/BloomrIO/v8go"
Running a script
ctx := v8.NewContext() // creates a new V8 context with a new Isolate aka VM
ctx.RunScript("const add = (a, b) => a + b", "math.js") // executes a script on the global context
ctx.RunScript("const result = add(3, 4)", "main.js") // any functions previously added to the context can be called
val, _ := ctx.RunScript("result", "value.js") // return a value in JavaScript back to Go
fmt.Printf("addition result: %s", val)
One VM, many contexts
iso := v8.NewIsolate() // creates a new JavaScript VM
ctx1 := v8.NewContext(iso) // new context within the VM
ctx1.RunScript("const multiply = (a, b) => a * b", "math.js")

ctx2 := v8.NewContext(iso) // another context on the same VM
if _, err := ctx2.RunScript("multiply(3, 4)", "main.js"); err != nil {
  // this will error as multiply is not defined in this context
}
JavaScript function with Go callback
iso := v8.NewIsolate() // create a new VM
// a template that represents a JS function
printfn := v8.NewFunctionTemplate(iso, func(info *v8.FunctionCallbackInfo) *v8.Value {
    fmt.Printf("%v", info.Args()) // when the JS function is called this Go callback will execute
    return nil // you can return a value back to the JS caller if required
})
global := v8.NewObjectTemplate(iso) // a template that represents a JS Object
global.Set("print", printfn) // sets the "print" property of the Object to our function
ctx := v8.NewContext(iso, global) // new Context with the global Object set to our object template
ctx.RunScript("print('foo')", "print.js") // will execute the Go callback with a single argunent 'foo'
Update a JavaScript object from Go
ctx := v8.NewContext() // new context with a default VM
obj := ctx.Global() // get the global object from the context
obj.Set("version", "v1.0.0") // set the property "version" on the object
val, _ := ctx.RunScript("version", "version.js") // global object will have the property set within the JS VM
fmt.Printf("version: %s", val)

if obj.Has("version") { // check if a property exists on the object
    obj.Delete("version") // remove the property from the object
}
JavaScript errors
val, err := ctx.RunScript(src, filename)
if err != nil {
  e := err.(*v8.JSError) // JavaScript errors will be returned as the JSError struct
  fmt.Println(e.Message) // the message of the exception thrown
  fmt.Println(e.Location) // the filename, line number and the column where the error occured
  fmt.Println(e.StackTrace) // the full stack trace of the error, if available

  fmt.Printf("javascript error: %v", e) // will format the standard error message
  fmt.Printf("javascript stack trace: %+v", e) // will format the full error stack trace
}
Pre-compile context-independent scripts to speed-up execution times

For scripts that are large or are repeatedly run in different contexts, it is beneficial to compile the script once and used the cached data from that compilation to avoid recompiling every time you want to run it.

source := "const multiply = (a, b) => a * b"
iso1 := v8.NewIsolate() // creates a new JavaScript VM
ctx1 := v8.NewContext(iso1) // new context within the VM
script1, _ := iso1.CompileUnboundScript(source, "math.js", v8.CompileOptions{}) // compile script to get cached data
val, _ := script1.Run(ctx1)

cachedData := script1.CreateCodeCache()

iso2 := v8.NewIsolate() // create a new JavaScript VM
ctx2 := v8.NewContext(iso2) // new context within the VM

script2, _ := iso2.CompileUnboundScript(source, "math.js", v8.CompileOptions{CachedData: cachedData}) // compile script in new isolate with cached data
val, _ = script2.Run(ctx2)
Terminate long running scripts
vals := make(chan *v8.Value, 1)
errs := make(chan error, 1)

go func() {
    val, err := ctx.RunScript(script, "forever.js") // exec a long running script
    if err != nil {
        errs <- err
        return
    }
    vals <- val
}()

select {
case val := <- vals:
    // success
case err := <- errs:
    // javascript error
case <- time.After(200 * time.Milliseconds):
    vm := ctx.Isolate() // get the Isolate from the context
    vm.TerminateExecution() // terminate the execution
    err := <- errs // will get a termination error back from the running script
}
CPU Profiler
func createProfile() {
	iso := v8.NewIsolate()
	ctx := v8.NewContext(iso)
	cpuProfiler := v8.NewCPUProfiler(iso)

	cpuProfiler.StartProfiling("my-profile")

	ctx.RunScript(profileScript, "script.js") # this script is defined in cpuprofiler_test.go
	val, _ := ctx.Global().Get("start")
	fn, _ := val.AsFunction()
	fn.Call(ctx.Global())

	cpuProfile := cpuProfiler.StopProfiling("my-profile")

	printTree("", cpuProfile.GetTopDownRoot()) # helper function to print the profile
}

func printTree(nest string, node *v8.CPUProfileNode) {
	fmt.Printf("%s%s %s:%d:%d\n", nest, node.GetFunctionName(), node.GetScriptResourceName(), node.GetLineNumber(), node.GetColumnNumber())
	count := node.GetChildrenCount()
	if count == 0 {
		return
	}
	nest = fmt.Sprintf("%s  ", nest)
	for i := 0; i < count; i++ {
		printTree(nest, node.GetChild(i))
	}
}

// Output
// (root) :0:0
//   (program) :0:0
//   start script.js:23:15
//     foo script.js:15:13
//       delay script.js:12:15
//         loop script.js:1:14
//       bar script.js:13:13
//         delay script.js:12:15
//           loop script.js:1:14
//       baz script.js:14:13
//         delay script.js:12:15
//           loop script.js:1:14
//   (garbage collector) :0:0

Documentation

Go Reference & more examples: https://pkg.go.dev/github.com/BloomrIO/v8go

Support

If you would like to ask questions about this library or want to keep up-to-date with the latest changes and releases, please join the #v8go channel on Gophers Slack. Click here to join the Gophers Slack community!

Windows

There used to be Windows binary support. For further information see, PR #234.

The v8go library would welcome contributions from anyone able to get an external windows build of the V8 library linking with v8go, using the version of V8 checked out in the deps/v8 git submodule, and documentation of the process involved. This process will likely involve passing a linker flag when building v8go (e.g. using the CGO_LDFLAGS environment variable.

V8 dependency

V8 version: 9.0.257.18 (April 2021)

In order to make v8go usable as a standard Go package, prebuilt static libraries of V8 are included for Linux and macOS. you should not require to build V8 yourself.

Due to security concerns of binary blobs hiding malicious code, the V8 binary is built via CI ONLY.

Project Goals

To provide a high quality, idiomatic, Go binding to the V8 C++ API.

The API should match the original API as closely as possible, but with an API that Gophers (Go enthusiasts) expect. For example: using multiple return values to return both result and error from a function, rather than throwing an exception.

This project also aims to keep up-to-date with the latest (stable) release of V8.

License

FOSSA Status

Development

Recompile V8 with debug info and debug checks

Aside from data races, Go should be memory-safe and v8go should preserve this property by adding the necessary checks to return an error or panic on these unsupported code paths. Release builds of v8go don't include debugging information for the V8 library since it significantly adds to the binary size, slows down compilation and shouldn't be needed by users of v8go. However, if a v8go bug causes a crash (e.g. during new feature development) then it can be helpful to build V8 with debugging information to get a C++ backtrace with line numbers. The following steps will not only do that, but also enable V8 debug checking, which can help with catching misuse of the V8 API.

  1. Make sure to clone the projects submodules (ie. the V8's depot_tools project): git submodule update --init --recursive
  2. Build the V8 binary for your OS: deps/build.py --debug. V8 is a large project, and building the binary can take up to 30 minutes.
  3. Build the executable to debug, using go build for commands or go test -c for tests. You may need to add the -ldflags=-compressdwarf=false option to disable debug information compression so this information can be read by the debugger (e.g. lldb that comes with Xcode v12.5.1, the latest Xcode released at the time of writing)
  4. Run the executable with a debugger (e.g. lldb -- ./v8go.test -test.run TestThatIsCrashing, run to start execution then use bt to print a bracktrace after it breaks on a crash), since backtraces printed by Go or V8 don't currently include line number information.
Upgrading the V8 binaries

We have the upgradev8 workflow. The workflow is triggered every day or manually.

If the current v8_version is different from the latest stable version, the workflow takes care of fetching the latest stable v8 files and copying them into deps/include. The last step of the workflow opens a new PR with the branch name v8_upgrade/<v8-version> with all the changes.

The next steps are:

  1. The build is not yet triggered automatically. To trigger it manually, go to the V8 Build Github Action, Select "Run workflow", and select your pushed branch eg. v8_upgrade/<v8-version>.
  2. Once built, this should open 3 PRs against your branch to add the libv8.a for Linux (for x86_64) and macOS for x86_64 and arm64; merge these PRs into your branch. You are now ready to raise the PR against master with the latest version of V8.
Flushing after C/C++ standard library printing for debugging

When using the C/C++ standard library functions for printing (e.g. printf), then the output will be buffered by default. This can cause some confusion, especially because the test binary (created through go test) does not flush the buffer at exit (at the time of writing). When standard output is the terminal, then it will use line buffering and flush when a new line is printed, otherwise (e.g. if the output is redirected to a pipe or file) it will be fully buffered and not even flush at the end of a line. When the test binary is executed through go test . (e.g. instead of separately compiled with go test -c and run with ./v8go.test) Go may redirect standard output internally, resulting in standard output being fully buffered.

A simple way to avoid this problem is to flush the standard output stream after printing with the fflush(stdout); statement. Not relying on the flushing at exit can also help ensure the output is printed before a crash.

Local leak checking

Leak checking is automatically done in CI, but it can be useful to do locally to debug leaks.

Leak checking is done using the Leak Sanitizer which is a part of LLVM. As such, compiling with clang as the C/C++ compiler seems to produce more complete backtraces (unfortunately still only of the system stack at the time of writing).

For instance, on a Debian-based Linux system, you can use sudo apt-get install clang-12 to install a recent version of clang. Then CC and CXX environment variables are needed to use that compiler. With that compiler, the tests can be run as follows

CC=clang-12 CXX=clang++-12 go test -c --tags leakcheck && ./v8go.test

The separate compile and link commands are currently needed to get line numbers in the backtrace.

On macOS, leak checking isn't available with the version of clang that comes with Xcode, so a separate compiler installation is needed. For example, with homebrew, brew install llvm will install a version of clang with support for this. The ASAN_OPTIONS environment variable will also be needed to run the code with leak checking enabled, since it isn't enabled by default on macOS. E.g. with the homebrew installation of llvm, the tests can be run with

CXX=/usr/local/opt/llvm/bin/clang++ CC=/usr/local/opt/llvm/bin/clang go test -c --tags leakcheck -ldflags=-compressdwarf=false
ASAN_OPTIONS=detect_leaks=1 ./v8go.test

The -ldflags=-compressdwarf=false is currently (with clang 13) needed to get line numbers in the backtrace.

Formatting

Go has go fmt, C has clang-format. Any changes to the v8go.h|cc should be formated with clang-format with the "Chromium" Coding style. This can be done easily by running the go generate command.

brew install clang-format to install on macOS.

V8 Gopher image based on original artwork from the amazing Renee French.

Documentation

Overview

Package v8go provides an API to execute JavaScript.

Index

Examples

Constants

This section is empty.

Variables

View Source 
var (
	CompileModeDefault = CompileMode(C.ScriptCompilerNoCompileOptions)
	CompileModeEager   = CompileMode(C.ScriptCompilerEagerCompile)
)

Functions

func JSONStringify 

func JSONStringify(ctx *Context, val Valuer) (string, error)

JSONStringify tries to stringify the JSON-serializable object value and returns it as string.

Example 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	ctx := v8.NewContext()
	defer ctx.Isolate().Dispose()
	defer ctx.Close()
	val, _ := v8.JSONParse(ctx, `{
		"a": 1,
		"b": "foo"
	}`)
	jsonStr, _ := v8.JSONStringify(ctx, val)
	fmt.Println(jsonStr)
}

Output:

{"a":1,"b":"foo"}

func SetFlags 

func SetFlags(flags ...string)

SetFlags sets flags for V8. For possible flags: https://github.com/v8/v8/blob/master/src/flags/flag-definitions.h Flags are expected to be prefixed with `--`, for example: `--harmony`. Flags can be reverted using the `--no` prefix equivalent, for example: `--use_strict` vs `--nouse_strict`. Flags will affect all Isolates created, even after creation.

func Version 

func Version() string

Version returns the version of the V8 Engine with the -v8go suffix

Types

type CPUProfile 

type CPUProfile struct {
	// contains filtered or unexported fields
}

func (*CPUProfile) Delete 

func (c *CPUProfile) Delete()

Deletes the profile and removes it from CpuProfiler's list. All pointers to nodes previously returned become invalid.

func (*CPUProfile) GetDuration 

func (c *CPUProfile) GetDuration() time.Duration

Returns the duration of the profile.

func (*CPUProfile) GetTitle 

func (c *CPUProfile) GetTitle() string

Returns CPU profile title.

func (*CPUProfile) GetTopDownRoot 

func (c *CPUProfile) GetTopDownRoot() *CPUProfileNode

Returns the root node of the top down call tree.

type CPUProfileNode 

type CPUProfileNode struct {
	// contains filtered or unexported fields
}

func (*CPUProfileNode) GetBailoutReason 

func (c *CPUProfileNode) GetBailoutReason() string

Returns the bailout reason for the function if the optimization was disabled for it.

func (*CPUProfileNode) GetChild 

func (c *CPUProfileNode) GetChild(index int) *CPUProfileNode

Retrieves a child node by index.

func (*CPUProfileNode) GetChildrenCount 

func (c *CPUProfileNode) GetChildrenCount() int

func (*CPUProfileNode) GetColumnNumber 

func (c *CPUProfileNode) GetColumnNumber() int

Returns number of the column where the function originates.

func (*CPUProfileNode) GetFunctionName 

func (c *CPUProfileNode) GetFunctionName() string

Returns function name (empty string for anonymous functions.)

func (*CPUProfileNode) GetHitCount 

func (c *CPUProfileNode) GetHitCount() int

Returns count of samples where the function was currently executing.

func (*CPUProfileNode) GetLineNumber 

func (c *CPUProfileNode) GetLineNumber() int

Returns number of the line where the function originates.

func (*CPUProfileNode) GetNodeId 

func (c *CPUProfileNode) GetNodeId() int

Returns node id.

func (*CPUProfileNode) GetParent 

func (c *CPUProfileNode) GetParent() *CPUProfileNode

Retrieves the ancestor node, or nil if the root.

func (*CPUProfileNode) GetScriptId 

func (c *CPUProfileNode) GetScriptId() int

Returns id for script from where the function originates.

func (*CPUProfileNode) GetScriptResourceName 

func (c *CPUProfileNode) GetScriptResourceName() string

Returns resource name for script from where the function originates.

type CPUProfiler 

type CPUProfiler struct {
	// contains filtered or unexported fields
}

func NewCPUProfiler 

func NewCPUProfiler(iso *Isolate) *CPUProfiler

CPUProfiler is used to control CPU profiling.

func (*CPUProfiler) Dispose 

func (c *CPUProfiler) Dispose()

Dispose will dispose the profiler.

func (*CPUProfiler) StartProfiling 

func (c *CPUProfiler) StartProfiling(title string)

StartProfiling starts collecting a CPU profile. Title may be an empty string. Several profiles may be collected at once. Attempts to start collecting several profiles with the same title are silently ignored.

func (*CPUProfiler) StopProfiling 

func (c *CPUProfiler) StopProfiling(title string) *CPUProfile

Stops collecting CPU profile with a given title and returns it. If the title given is empty, finishes the last profile started.

type CompileMode 

type CompileMode C.int

type CompileOptions 

type CompileOptions struct {
	CachedData *CompilerCachedData

	Mode CompileMode
}

type CompilerCachedData 

type CompilerCachedData struct {
	Bytes    []byte
	Rejected bool
}

type Context 

type Context struct {
	// contains filtered or unexported fields
}

Context is a global root execution environment that allows separate, unrelated, JavaScript applications to run in a single instance of V8.

Example 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	ctx := v8.NewContext()
	defer ctx.Isolate().Dispose()
	defer ctx.Close()
	ctx.RunScript("const add = (a, b) => a + b", "math.js")
	ctx.RunScript("const result = add(3, 4)", "main.js")
	val, _ := ctx.RunScript("result", "value.js")
	fmt.Println(val)
}

Output:

7
Example (GlobalTemplate) 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	iso := v8.NewIsolate()
	defer iso.Dispose()
	obj := v8.NewObjectTemplate(iso)
	obj.Set("version", "v1.0.0")
	ctx := v8.NewContext(iso, obj)
	defer ctx.Close()
	val, _ := ctx.RunScript("version", "main.js")
	fmt.Println(val)
}

Output:

v1.0.0
Example (Isolate) 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	iso := v8.NewIsolate()
	defer iso.Dispose()
	ctx1 := v8.NewContext(iso)
	defer ctx1.Close()
	ctx1.RunScript("const foo = 'bar'", "context_one.js")
	val, _ := ctx1.RunScript("foo", "foo.js")
	fmt.Println(val)

	ctx2 := v8.NewContext(iso)
	defer ctx2.Close()
	_, err := ctx2.RunScript("foo", "context_two.js")
	fmt.Println(err)
}

Output:

bar
ReferenceError: foo is not defined

func NewContext 

func NewContext(opt ...ContextOption) *Context

NewContext creates a new JavaScript context; if no Isolate is passed as a ContextOption than a new Isolate will be created.

func (*Context) Close 

func (c *Context) Close()

Close will dispose the context and free the memory. Access to any values associated with the context after calling Close may panic.

func (*Context) Global 

func (c *Context) Global() *Object

Global returns the global proxy object. Global proxy object is a thin wrapper whose prototype points to actual context's global object with the properties like Object, etc. This is done that way for security reasons. Please note that changes to global proxy object prototype most probably would break the VM — V8 expects only global object as a prototype of global proxy object.

func (*Context) Isolate 

func (c *Context) Isolate() *Isolate

Isolate gets the current context's parent isolate.

func (*Context) PerformMicrotaskCheckpoint 

func (c *Context) PerformMicrotaskCheckpoint()

PerformMicrotaskCheckpoint runs the default MicrotaskQueue until empty. This is used to make progress on Promises.

func (*Context) RetainedValueCount 

func (c *Context) RetainedValueCount() int

func (*Context) RunScript 

func (c *Context) RunScript(source string, origin string) (*Value, error)

RunScript executes the source JavaScript; origin (a.k.a. filename) provides a reference for the script and used in the stack trace if there is an error. error will be of type `JSError` if not nil.

type ContextOption 

type ContextOption interface {
	// contains filtered or unexported methods
}

ContextOption sets options such as Isolate and Global Template to the NewContext

type Function 

type Function struct {
	*Value
}

Function is a JavaScript function.

func (*Function) Call 

func (fn *Function) Call(recv Valuer, args ...Valuer) (*Value, error)

Call this JavaScript function with the given arguments.

func (*Function) NewInstance 

func (fn *Function) NewInstance(args ...Valuer) (*Object, error)

Invoke a constructor function to create an object instance.

func (*Function) SourceMapUrl 

func (fn *Function) SourceMapUrl() *Value

Return the source map url for a function.

type FunctionCallback 

type FunctionCallback func(info *FunctionCallbackInfo) *Value

FunctionCallback is a callback that is executed in Go when a function is executed in JS.

type FunctionCallbackInfo 

type FunctionCallbackInfo struct {
	// contains filtered or unexported fields
}

FunctionCallbackInfo is the argument that is passed to a FunctionCallback.

func (*FunctionCallbackInfo) Args 

func (i *FunctionCallbackInfo) Args() []*Value

Args returns a slice of the value arguments that are passed to the JS function.

func (*FunctionCallbackInfo) Context 

func (i *FunctionCallbackInfo) Context() *Context

Context is the current context that the callback is being executed in.

func (*FunctionCallbackInfo) Release 

func (i *FunctionCallbackInfo) Release()

func (*FunctionCallbackInfo) This 

func (i *FunctionCallbackInfo) This() *Object

This returns the receiver object "this".

type FunctionTemplate 

type FunctionTemplate struct {
	// contains filtered or unexported fields
}

FunctionTemplate is used to create functions at runtime. There can only be one function created from a FunctionTemplate in a context. The lifetime of the created function is equal to the lifetime of the context.

Example 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	iso := v8.NewIsolate()
	defer iso.Dispose()
	global := v8.NewObjectTemplate(iso)
	printfn := v8.NewFunctionTemplate(iso, func(info *v8.FunctionCallbackInfo) *v8.Value {
		fmt.Printf("%+v\n", info.Args())
		return nil
	})
	global.Set("print", printfn, v8.ReadOnly)
	ctx := v8.NewContext(iso, global)
	defer ctx.Close()
	ctx.RunScript("print('foo', 'bar', 0, 1)", "")
}

Output:

[foo bar 0 1]
Example (Fetch) 
package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"strings"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	iso := v8.NewIsolate()
	defer iso.Dispose()
	global := v8.NewObjectTemplate(iso)

	fetchfn := v8.NewFunctionTemplate(iso, func(info *v8.FunctionCallbackInfo) *v8.Value {
		args := info.Args()
		url := args[0].String()

		resolver, _ := v8.NewPromiseResolver(info.Context())

		go func() {
			res, _ := http.Get(url)
			body, _ := ioutil.ReadAll(res.Body)
			val, _ := v8.NewValue(iso, string(body))
			resolver.Resolve(val)
		}()
		return resolver.GetPromise().Value
	})
	global.Set("fetch", fetchfn, v8.ReadOnly)

	ctx := v8.NewContext(iso, global)
	defer ctx.Close()
	val, _ := ctx.RunScript("fetch('https://github.com/BloomrIO/v8go')", "")
	prom, _ := val.AsPromise()

	// wait for the promise to resolve
	for prom.State() == v8.Pending {
		continue
	}
	fmt.Printf("%s\n", strings.Split(prom.Result().String(), "\n")[0])
}

Output:

<!DOCTYPE html>

func NewFunctionTemplate 

func NewFunctionTemplate(iso *Isolate, callback FunctionCallback) *FunctionTemplate

NewFunctionTemplate creates a FunctionTemplate for a given callback.

func (*FunctionTemplate) GetFunction 

func (tmpl *FunctionTemplate) GetFunction(ctx *Context) *Function

GetFunction returns an instance of this function template bound to the given context.

func (FunctionTemplate) Set 

func (t FunctionTemplate) Set(name string, val interface{}, attributes ...PropertyAttribute) error

Set adds a property to each instance created by this template. The property must be defined either as a primitive value, or a template. If the value passed is a Go supported primitive (string, int32, uint32, int64, uint64, float64, big.Int) then a value will be created and set as the value property.

type HeapStatistics 

type HeapStatistics struct {
	TotalHeapSize            uint64
	TotalHeapSizeExecutable  uint64
	TotalPhysicalSize        uint64
	TotalAvailableSize       uint64
	UsedHeapSize             uint64
	HeapSizeLimit            uint64
	MallocedMemory           uint64
	ExternalMemory           uint64
	PeakMallocedMemory       uint64
	NumberOfNativeContexts   uint64
	NumberOfDetachedContexts uint64
}

HeapStatistics represents V8 isolate heap statistics

type Isolate 

type Isolate struct {
	// contains filtered or unexported fields
}

Isolate is a JavaScript VM instance with its own heap and garbage collector. Most applications will create one isolate with many V8 contexts for execution.

func NewIsolate 

func NewIsolate() *Isolate

NewIsolate creates a new V8 isolate. Only one thread may access a given isolate at a time, but different threads may access different isolates simultaneously. When an isolate is no longer used its resources should be freed by calling iso.Dispose(). An *Isolate can be used as a v8go.ContextOption to create a new Context, rather than creating a new default Isolate.

func (*Isolate) Close deprecated 

func (i *Isolate) Close()

Deprecated: use `iso.Dispose()`.

func (*Isolate) CompileUnboundScript 

func (i *Isolate) CompileUnboundScript(source, origin string, opts CompileOptions) (*UnboundScript, error)

CompileUnboundScript will create an UnboundScript (i.e. context-indepdent) using the provided source JavaScript, origin (a.k.a. filename), and options. If options contain a non-null CachedData, compilation of the script will use that code cache. error will be of type `JSError` if not nil.

func (*Isolate) Dispose 

func (i *Isolate) Dispose()

Dispose will dispose the Isolate VM; subsequent calls will panic.

func (*Isolate) GetHeapStatistics 

func (i *Isolate) GetHeapStatistics() HeapStatistics

GetHeapStatistics returns heap statistics for an isolate.

func (*Isolate) IsExecutionTerminating 

func (i *Isolate) IsExecutionTerminating() bool

IsExecutionTerminating returns whether V8 is currently terminating Javascript execution. If true, there are still JavaScript frames on the stack and the termination exception is still active.

func (*Isolate) TerminateExecution 

func (i *Isolate) TerminateExecution()

TerminateExecution terminates forcefully the current thread of JavaScript execution in the given isolate.

func (*Isolate) ThrowException 

func (i *Isolate) ThrowException(value *Value) *Value

ThrowException schedules an exception to be thrown when returning to JavaScript. When an exception has been scheduled it is illegal to invoke any JavaScript operation; the caller must return immediately and only after the exception has been handled does it become legal to invoke JavaScript operations.

type JSError 

type JSError struct {
	Message    string
	Location   string
	StackTrace string
}

JSError is an error that is returned if there is are any JavaScript exceptions handled in the context. When used with the fmt verb `%+v`, will output the JavaScript stack trace, if available.

func (*JSError) Error 

func (e *JSError) Error() string

func (*JSError) Format 

func (e *JSError) Format(s fmt.State, verb rune)

Format implements the fmt.Formatter interface to provide a custom formatter primarily to output the javascript stack trace with %+v

type Object 

type Object struct {
	*Value
}

Object is a JavaScript object (ECMA-262, 4.3.3)

Example (Global) 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	iso := v8.NewIsolate()
	defer iso.Dispose()
	ctx := v8.NewContext(iso)
	defer ctx.Close()
	global := ctx.Global()

	console := v8.NewObjectTemplate(iso)
	logfn := v8.NewFunctionTemplate(iso, func(info *v8.FunctionCallbackInfo) *v8.Value {
		fmt.Println(info.Args()[0])
		return nil
	})
	console.Set("log", logfn)
	consoleObj, _ := console.NewInstance(ctx)

	global.Set("console", consoleObj)
	ctx.RunScript("console.log('foo')", "")
}

Output:

foo

func (*Object) Delete 

func (o *Object) Delete(key string) bool

Delete returns true if successful in deleting a named property on the object.

func (*Object) DeleteIdx 

func (o *Object) DeleteIdx(idx uint32) bool

DeleteIdx returns true if successful in deleting a value at a given index of the object.

func (*Object) Get 

func (o *Object) Get(key string) (*Value, error)

Get tries to get a Value for a given Object property key.

func (*Object) GetIdx 

func (o *Object) GetIdx(idx uint32) (*Value, error)

GetIdx tries to get a Value at a give Object index.

func (*Object) GetInternalField 

func (o *Object) GetInternalField(idx uint32) *Value

GetInternalField gets the Value set by SetInternalField for the given index or the JS undefined value if the index hadn't been set. Panics if given an out of range index.

func (*Object) Has 

func (o *Object) Has(key string) bool

Has calls the abstract operation HasProperty(O, P) described in ECMA-262, 7.3.10. Returns true, if the object has the property, either own or on the prototype chain.

func (*Object) HasIdx 

func (o *Object) HasIdx(idx uint32) bool

HasIdx returns true if the object has a value at the given index.

func (*Object) InternalFieldCount 

func (o *Object) InternalFieldCount() uint32

InternalFieldCount returns the number of internal fields this Object has.

func (*Object) MethodCall 

func (o *Object) MethodCall(methodName string, args ...Valuer) (*Value, error)

func (*Object) Set 

func (o *Object) Set(key string, val interface{}) error

Set will set a property on the Object to a given value. Supports all value types, eg: Object, Array, Date, Set, Map etc If the value passed is a Go supported primitive (string, int32, uint32, int64, uint64, float64, big.Int) then a *Value will be created and set as the value property.

func (*Object) SetIdx 

func (o *Object) SetIdx(idx uint32, val interface{}) error

Set will set a given index on the Object to a given value. Supports all value types, eg: Object, Array, Date, Set, Map etc If the value passed is a Go supported primitive (string, int32, uint32, int64, uint64, float64, big.Int) then a *Value will be created and set as the value property.

func (*Object) SetInternalField 

func (o *Object) SetInternalField(idx uint32, val interface{}) error

SetInternalField sets the value of an internal field for an ObjectTemplate instance. Panics if the index isn't in the range set by (*ObjectTemplate).SetInternalFieldCount.

type ObjectTemplate 

type ObjectTemplate struct {
	// contains filtered or unexported fields
}

ObjectTemplate is used to create objects at runtime. Properties added to an ObjectTemplate are added to each object created from the ObjectTemplate.

func NewObjectTemplate 

func NewObjectTemplate(iso *Isolate) *ObjectTemplate

NewObjectTemplate creates a new ObjectTemplate. The *ObjectTemplate can be used as a v8go.ContextOption to create a global object in a Context.

func (*ObjectTemplate) InternalFieldCount 

func (o *ObjectTemplate) InternalFieldCount() uint32

InternalFieldCount returns the number of internal fields that instances of this template will have.

func (*ObjectTemplate) NewInstance 

func (o *ObjectTemplate) NewInstance(ctx *Context) (*Object, error)

NewInstance creates a new Object based on the template.

func (ObjectTemplate) Set 

func (t ObjectTemplate) Set(name string, val interface{}, attributes ...PropertyAttribute) error

Set adds a property to each instance created by this template. The property must be defined either as a primitive value, or a template. If the value passed is a Go supported primitive (string, int32, uint32, int64, uint64, float64, big.Int) then a value will be created and set as the value property.

func (*ObjectTemplate) SetInternalFieldCount 

func (o *ObjectTemplate) SetInternalFieldCount(fieldCount uint32)

SetInternalFieldCount sets the number of internal fields that instances of this template will have.

type Promise 

type Promise struct {
	*Object
}

Promise is the JavaScript promise object defined in ES6

func (*Promise) Catch 

func (p *Promise) Catch(cb FunctionCallback) *Promise

Catch invokes the given function if the promise is rejected. See Then for other details.

func (*Promise) Result 

func (p *Promise) Result() *Value

Result is the value result of the Promise. The Promise must NOT be in a Pending state, otherwise may panic. Call promise.State() to validate state before calling for the result.

func (*Promise) State 

func (p *Promise) State() PromiseState

State returns the current state of the Promise.

func (*Promise) Then 

func (p *Promise) Then(cbs ...FunctionCallback) *Promise

Then accepts 1 or 2 callbacks. The first is invoked when the promise has been fulfilled. The second is invoked when the promise has been rejected. The returned Promise resolves after the callback finishes execution.

V8 only invokes the callback when processing "microtasks". The default MicrotaskPolicy processes them when the call depth decreases to 0. Call (*Context).PerformMicrotaskCheckpoint to trigger it manually.

type PromiseResolver 

type PromiseResolver struct {
	*Object
	// contains filtered or unexported fields
}

PromiseResolver is the resolver object for the promise. Most cases will create a new PromiseResolver and return the associated Promise from the resolver.

func NewPromiseResolver 

func NewPromiseResolver(ctx *Context) (*PromiseResolver, error)

NewPromiseResolver creates a new Promise resolver for the given context. The associated Promise will be in a Pending state.

func (*PromiseResolver) GetPromise 

func (r *PromiseResolver) GetPromise() *Promise

GetPromise returns the associated Promise object for this resolver. The Promise object is unique to the resolver and returns the same object on multiple calls.

func (*PromiseResolver) Reject 

func (r *PromiseResolver) Reject(err *Value) bool

Reject invokes the Promise reject state with the given value. The Promise state will transition from Pending to Rejected.

func (*PromiseResolver) Resolve 

func (r *PromiseResolver) Resolve(val Valuer) bool

Resolve invokes the Promise resolve state with the given value. The Promise state will transition from Pending to Fulfilled.

type PromiseState 

type PromiseState int

PromiseState is the state of the Promise. 

const (
	Pending PromiseState = iota
	Fulfilled
	Rejected
)

type PropertyAttribute 

type PropertyAttribute uint8

PropertyAttribute are the attribute flags for a property on an Object. Typical usage when setting an Object or TemplateObject property, and can also be validated when accessing a property. 

const (
	// None.
	None PropertyAttribute = 0
	// ReadOnly, ie. not writable.
	ReadOnly PropertyAttribute = 1 << iota
	// DontEnum, ie. not enumerable.
	DontEnum
	// DontDelete, ie. not configurable.
	DontDelete
)

type UnboundScript 

type UnboundScript struct {
	// contains filtered or unexported fields
}

func (*UnboundScript) CreateCodeCache 

func (u *UnboundScript) CreateCodeCache() *CompilerCachedData

Create a code cache from the unbound script.

func (*UnboundScript) Run 

func (u *UnboundScript) Run(ctx *Context) (*Value, error)

Run will bind the unbound script to the provided context and run it. If the context provided does not belong to the same isolate that the script was compiled in, Run will panic. If an error occurs, it will be of type `JSError`.

type Value 

type Value struct {
	// contains filtered or unexported fields
}

Value represents all Javascript values and objects

func JSONParse 

func JSONParse(ctx *Context, str string) (*Value, error)

JSONParse tries to parse the string and returns it as *Value if successful. Any JS errors will be returned as `JSError`.

Example 
package main

import (
	"fmt"

	v8 "github.com/BloomrIO/v8go"
)

func main() {
	ctx := v8.NewContext()
	defer ctx.Isolate().Dispose()
	defer ctx.Close()
	val, _ := v8.JSONParse(ctx, `{"foo": "bar"}`)
	fmt.Println(val)
}

Output:

[object Object]

func NewValue 

func NewValue(iso *Isolate, val interface{}) (*Value, error)

NewValue will create a primitive value. Supported values types to create are: 

string -> V8::String
int32 -> V8::Integer
uint32 -> V8::Integer
int64 -> V8::BigInt
uint64 -> V8::BigInt
bool -> V8::Boolean
*big.Int -> V8::BigInt

func Null 

func Null(iso *Isolate) *Value

Null returns the `null` JS value

func Undefined 

func Undefined(iso *Isolate) *Value

Undefined returns the `undefined` JS value

func (*Value) ArrayIndex 

func (v *Value) ArrayIndex() (idx uint32, ok bool)

ArrayIndex attempts to converts a string to an array index. Returns ok false if conversion fails.

func (*Value) AsFunction 

func (v *Value) AsFunction() (*Function, error)

func (*Value) AsObject 

func (v *Value) AsObject() (*Object, error)

AsObject will cast the value to the Object type. If the value is not an Object then an error is returned. Use `value.Object()` to do the JS equivalent of `Object(value)`.

func (*Value) AsPromise 

func (v *Value) AsPromise() (*Promise, error)

func (*Value) BigInt 

func (v *Value) BigInt() *big.Int

BigInt perform the equivalent of `BigInt(value)` in JS.

func (*Value) Boolean 

func (v *Value) Boolean() bool

Boolean perform the equivalent of `Boolean(value)` in JS. This can never fail.

func (*Value) DetailString 

func (v *Value) DetailString() string

DetailString provide a string representation of this value usable for debugging.

func (*Value) Format 

func (v *Value) Format(s fmt.State, verb rune)

Format implements the fmt.Formatter interface to provide a custom formatter primarily to output the detail string (for debugging) with `%+v` verb.

func (*Value) Int32 

func (v *Value) Int32() int32

Int32 perform the equivalent of `Number(value)` in JS and convert the result to a signed 32-bit integer by performing the steps in https://tc39.es/ecma262/#sec-toint32.

func (*Value) Integer 

func (v *Value) Integer() int64

Integer perform the equivalent of `Number(value)` in JS and convert the result to an integer. Negative values are rounded up, positive values are rounded down. NaN is converted to 0. Infinite values yield undefined results.

func (*Value) IsArgumentsObject 

func (v *Value) IsArgumentsObject() bool

IsArgumentsObject returns true if this value is an Arguments object.

func (*Value) IsArray 

func (v *Value) IsArray() bool

IsArray returns true if this value is an array. Note that it will return false for a `Proxy` of an array.

func (*Value) IsArrayBuffer 

func (v *Value) IsArrayBuffer() bool

IsArrayBuffer returns true if this value is an `ArrayBuffer`.

func (*Value) IsArrayBufferView 

func (v *Value) IsArrayBufferView() bool

IsArrayBufferView returns true if this value is an `ArrayBufferView`.

func (*Value) IsAsyncFunction 

func (v *Value) IsAsyncFunction() bool

IsAsyncFunc returns true if this value is an async function.

func (*Value) IsBigInt 

func (v *Value) IsBigInt() bool

IsBigInt returns true if this value is a bigint. This is equivalent to `typeof value === 'bigint'` in JS.

func (*Value) IsBigInt64Array 

func (v *Value) IsBigInt64Array() bool

IsBigInt64Array returns true if this value is a `BigInt64Array`.

func (*Value) IsBigIntObject 

func (v *Value) IsBigIntObject() bool

IsBigIntObject returns true if this value is a BigInt object.

func (*Value) IsBigUint64Array 

func (v *Value) IsBigUint64Array() bool

IsBigUint64Array returns true if this value is a BigUint64Array`.

func (*Value) IsBoolean 

func (v *Value) IsBoolean() bool

IsBoolean returns true if this value is boolean. This is equivalent to `typeof value === 'boolean'` in JS.

func (*Value) IsDataView 

func (v *Value) IsDataView() bool

IsDataView returns true if this value is a `DataView`.

func (*Value) IsDate 

func (v *Value) IsDate() bool

IsDate returns true if this value is a `Date`.

func (*Value) IsExternal 

func (v *Value) IsExternal() bool

IsExternal returns true if this value is an `External` object.

func (*Value) IsFalse 

func (v *Value) IsFalse() bool

IsFalse returns true if this value is false. This is not the same as `!BooleanValue()`. The latter performs a conversion to boolean, i.e. the result of `!Boolean(value)` in JS, whereas this checks `value === false`.

func (*Value) IsFloat32Array 

func (v *Value) IsFloat32Array() bool

IsFloat32Array returns true if this value is a `Float32Array`.

func (*Value) IsFloat64Array 

func (v *Value) IsFloat64Array() bool

IsFloat64Array returns true if this value is a `Float64Array`.

func (*Value) IsFunction 

func (v *Value) IsFunction() bool

IsFunction returns true if this value is a function. This is equivalent to `typeof value === 'function'` in JS.

func (*Value) IsGeneratorFunction 

func (v *Value) IsGeneratorFunction() bool

Is IsGeneratorFunc returns true if this value is a Generator function.

func (*Value) IsGeneratorObject 

func (v *Value) IsGeneratorObject() bool

IsGeneratorObject returns true if this value is a Generator object (iterator).

func (*Value) IsInt16Array 

func (v *Value) IsInt16Array() bool

IsInt16Array returns true if this value is an `Int16Array`.

func (*Value) IsInt32 

func (v *Value) IsInt32() bool

IsInt32 returns true if this value is a 32-bit signed integer.

func (*Value) IsInt32Array 

func (v *Value) IsInt32Array() bool

IsInt32Array returns true if this value is an `Int32Array`.

func (*Value) IsInt8Array 

func (v *Value) IsInt8Array() bool

IsInt8Array returns true if this value is an `Int8Array`.

func (*Value) IsMap 

func (v *Value) IsMap() bool

IsMap returns true if this value is a `Map`.

func (*Value) IsMapIterator 

func (v *Value) IsMapIterator() bool

IsMapIterator returns true if this value is a `Map` Iterator.

func (*Value) IsModuleNamespaceObject 

func (v *Value) IsModuleNamespaceObject() bool

IsModuleNamespaceObject returns true if the value is a `Module` Namespace `Object`.

func (*Value) IsName 

func (v *Value) IsName() bool

IsName returns true if this value is a symbol or a string. This is equivalent to `typeof value === 'string' || typeof value === 'symbol'` in JS.

func (*Value) IsNativeError 

func (v *Value) IsNativeError() bool

IsNativeError returns true if this value is a NativeError.

func (*Value) IsNull 

func (v *Value) IsNull() bool

IsNull returns true if this value is the null value. See ECMA-262 4.3.11.

func (*Value) IsNullOrUndefined 

func (v *Value) IsNullOrUndefined() bool

IsNullOrUndefined returns true if this value is either the null or the undefined value. See ECMA-262 4.3.11. and 4.3.12 This is equivalent to `value == null` in JS.

func (*Value) IsNumber 

func (v *Value) IsNumber() bool

IsNumber returns true if this value is a number. This is equivalent to `typeof value === 'number'` in JS.

func (*Value) IsNumberObject 

func (v *Value) IsNumberObject() bool

IsNumberObject returns true if this value is a `Number` object.

func (*Value) IsObject 

func (v *Value) IsObject() bool

IsObject returns true if this value is an object.

func (*Value) IsPromise 

func (v *Value) IsPromise() bool

IsPromise returns true if this value is a `Promise`.

func (*Value) IsProxy 

func (v *Value) IsProxy() bool

IsProxy returns true if this value is a JavaScript `Proxy`.

func (*Value) IsRegExp 

func (v *Value) IsRegExp() bool

IsRegExp returns true if this value is a `RegExp`.

func (*Value) IsSet 

func (v *Value) IsSet() bool

IsSet returns true if this value is a `Set`.

func (*Value) IsSetIterator 

func (v *Value) IsSetIterator() bool

IsSetIterator returns true if this value is a `Set` Iterator.

func (*Value) IsSharedArrayBuffer 

func (v *Value) IsSharedArrayBuffer() bool

IsSharedArrayBuffer returns true if this value is a `SharedArrayBuffer`.

func (*Value) IsString 

func (v *Value) IsString() bool

IsString returns true if this value is an instance of the String type. See ECMA-262 8.4. This is equivalent to `typeof value === 'string'` in JS.

func (*Value) IsStringObject 

func (v *Value) IsStringObject() bool

IsStringObject returns true if this value is a `String` object.

func (*Value) IsSymbol 

func (v *Value) IsSymbol() bool

IsSymbol returns true if this value is a symbol. This is equivalent to `typeof value === 'symbol'` in JS.

func (*Value) IsSymbolObject 

func (v *Value) IsSymbolObject() bool

IsSymbolObject returns true if this value is a `Symbol` object.

func (*Value) IsTrue 

func (v *Value) IsTrue() bool

IsTrue returns true if this value is true. This is not the same as `BooleanValue()`. The latter performs a conversion to boolean, i.e. the result of `Boolean(value)` in JS, whereas this checks `value === true`.

func (*Value) IsTypedArray 

func (v *Value) IsTypedArray() bool

IsTypedArray returns true if this value is one of TypedArrays.

func (*Value) IsUint16Array 

func (v *Value) IsUint16Array() bool

IsUint16Array returns true if this value is an `Uint16Array`.

func (*Value) IsUint32 

func (v *Value) IsUint32() bool

IsUint32 returns true if this value is a 32-bit unsigned integer.

func (*Value) IsUint32Array 

func (v *Value) IsUint32Array() bool

IsUint32Array returns true if this value is an `Uint32Array`.

func (*Value) IsUint8Array 

func (v *Value) IsUint8Array() bool

IsUint8Array returns true if this value is an `Uint8Array`.

func (*Value) IsUint8ClampedArray 

func (v *Value) IsUint8ClampedArray() bool

IsUint8ClampedArray returns true if this value is an `Uint8ClampedArray`.

func (*Value) IsUndefined 

func (v *Value) IsUndefined() bool

IsUndefined returns true if this value is the undefined value. See ECMA-262 4.3.10.

func (*Value) IsWasmModuleObject 

func (v *Value) IsWasmModuleObject() bool

IsWasmModuleObject returns true if this value is a `WasmModuleObject`.

func (*Value) IsWeakMap 

func (v *Value) IsWeakMap() bool

IsWeakMap returns true if this value is a `WeakMap`.

func (*Value) IsWeakSet 

func (v *Value) IsWeakSet() bool

IsWeakSet returns true if this value is a `WeakSet`.

func (*Value) MarshalJSON 

func (v *Value) MarshalJSON() ([]byte, error)

MarshalJSON implements the json.Marshaler interface.

func (*Value) Number 

func (v *Value) Number() float64

Number perform the equivalent of `Number(value)` in JS.

func (*Value) Object 

func (v *Value) Object() *Object

Object perform the equivalent of Object(value) in JS. To just cast this value as an Object use AsObject() instead.

func (*Value) Release 

func (v *Value) Release()

Release this value. Using the value after calling this function will result in undefined behavior.

func (*Value) SameValue 

func (v *Value) SameValue(other *Value) bool

SameValue returns true if the other value is the same value. This is equivalent to `Object.is(v, other)` in JS.

func (*Value) SharedArrayBufferGetContents 

func (v *Value) SharedArrayBufferGetContents() ([]byte, func(), error)

func (*Value) String 

func (v *Value) String() string

String perform the equivalent of `String(value)` in JS. Primitive values are returned as-is, objects will return `[object Object]` and functions will print their definition.

func (*Value) Uint32 

func (v *Value) Uint32() uint32

Uint32 perform the equivalent of `Number(value)` in JS and convert the result to an unsigned 32-bit integer by performing the steps in https://tc39.es/ecma262/#sec-touint32.

type Valuer 

type Valuer interface {
	// contains filtered or unexported methods
}

Valuer is an interface that reperesents anything that extends from a Value eg. Object, Array, Date etc

Source Files

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Directories

Path Synopsis
deps
darwin_arm64
Package darwin_arm64 is required to provide support for vendoring modules DO NOT REMOVE
 Package darwin_arm64 is required to provide support for vendoring modules DO NOT REMOVE
darwin_x86_64
Package darwin_x86_64 is required to provide support for vendoring modules DO NOT REMOVE
 Package darwin_x86_64 is required to provide support for vendoring modules DO NOT REMOVE
include
Generated by deps/upgrade_v8.py, DO NOT REMOVE/EDIT MANUALLY.
 Generated by deps/upgrade_v8.py, DO NOT REMOVE/EDIT MANUALLY.
include/cppgc
Generated by deps/upgrade_v8.py, DO NOT REMOVE/EDIT MANUALLY.
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include/libplatform
Generated by deps/upgrade_v8.py, DO NOT REMOVE/EDIT MANUALLY.
 Generated by deps/upgrade_v8.py, DO NOT REMOVE/EDIT MANUALLY.
linux_arm64
Package linux_arm64 is required to provide support for vendoring modules DO NOT REMOVE
 Package linux_arm64 is required to provide support for vendoring modules DO NOT REMOVE
linux_x86_64
Package linux_x86_64 is required to provide support for vendoring modules DO NOT REMOVE
 Package linux_x86_64 is required to provide support for vendoring modules DO NOT REMOVE

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