fetch

README

WASM-FETCH

A go-wasm library that wraps the Fetch API

Install

go get marwan.io/wasm-fetch

Motivation

Importing net/http adds ~4 MBs to your wasm binary. If that's an issue for you, you can use this library to make fetch calls.

Example

package main

import (
    "context"
    "time"

    "marwan.io/wasm-fetch"
)

ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
resp, err := fetch.Fetch("/some/api/call", &fetch.Opts{
    Body:   strings.NewReader(`{"one": "two"}`),
    Method: fetch.MethodPost,
    Signal: ctx,
})
// use response...

Status

GO-WASM is currently experimental and therefore this package is experimental as well, things can break unexpectedly.

Documentation

Overview

Package fetch is a Web Assembly fetch wrapper that avoids importing net/http.

package main

import (
	"context"
	"time"

	"marwan.io/wasm-fetch"
)

ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
resp, err := fetch.Fetch("/some/api/call", &fetch.Opts{
	Body:   strings.NewReader(`{"one": "two"}`),
	Method: fetch.MethodPost,
	Signal: ctx,
})

Index

• Constants
• func CanonicalHeaderKey(s string) string
• type Header
  • func (h Header) Add(key, value string)
  • func (h Header) Del(key string)
  • func (h Header) Get(key string) string
  • func (h Header) Set(key, value string)
  • func (h Header) Write(w io.Writer) error
  • func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error
• type Opts
• type Response
  • func Fetch(url string, opts *Opts) (*Response, error)

Constants

const (
	CacheDefault      = "default"
	CacheNoStore      = "no-store"
	CacheReload       = "reload"
	CacheNone         = "no-cache"
	CacheForce        = "force-cache"
	CacheOnlyIfCached = "only-if-cached"
)

cache enums

const (
	CredentialsOmit       = "omit"
	CredentialsSameOrigin = "same-origin"
	CredentialsInclude    = "include"
)

credentials enums

const (
	MethodGet     = "GET"
	MethodHead    = "HEAD"
	MethodPost    = "POST"
	MethodPut     = "PUT"
	MethodPatch   = "PATCH" // RFC 5789
	MethodDelete  = "DELETE"
	MethodConnect = "CONNECT"
	MethodOptions = "OPTIONS"
	MethodTrace   = "TRACE"
)

Common HTTP methods.

Unless otherwise noted, these are defined in RFC 7231 section 4.3.

const (
	ModeSameOrigin = "same-origin"
	ModeNoCORS     = "no-cors"
	ModeCORS       = "cors"
	ModeNavigate   = "navigate"
)

Mode enums

const (
	RedirectFollow = "follow"
	RedirectError  = "error"
	RedirectManual = "manual"
)

Redirect enums

const (
	ReferrerNone   = "no-referrer"
	ReferrerClient = "client"
)

Referrer enums

const (
	ReferrerPolicyNone        = "no-referrer"
	ReferrerPolicyNoDowngrade = "no-referrer-when-downgrade"
	ReferrerPolicyOrigin      = "origin"
	ReferrerPolicyCrossOrigin = "origin-when-cross-origin"
	ReferrerPolicyUnsafeURL   = "unsafe-url"
)

ReferrerPolicy enums

Functions

func CanonicalHeaderKey

func CanonicalHeaderKey(s string) string

CanonicalHeaderKey returns the canonical format of the header key s. The canonicalization converts the first letter and any letter following a hyphen to upper case; the rest are converted to lowercase. For example, the canonical key for "accept-encoding" is "Accept-Encoding". If s contains a space or invalid header field bytes, it is returned without modifications.

Types

type Header

type Header map[string][]string

A Header represents the key-value pairs in an HTTP header.

func (Header) Add

func (h Header) Add(key, value string)

Add adds the key, value pair to the header. It appends to any existing values associated with key.

func (Header) Del

func (h Header) Del(key string)

Del deletes the values associated with key.

func (Header) Get

func (h Header) Get(key string) string

Get gets the first value associated with the given key. It is case insensitive; textproto.CanonicalMIMEHeaderKey is used to canonicalize the provided key. If there are no values associated with the key, Get returns "". To access multiple values of a key, or to use non-canonical keys, access the map directly.

func (Header) Set

func (h Header) Set(key, value string)

Set sets the header entries associated with key to the single element value. It replaces any existing values associated with key.

func (Header) Write

func (h Header) Write(w io.Writer) error

Write writes a header in wire format.

func (Header) WriteSubset

func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error

WriteSubset writes a header in wire format. If exclude is not nil, keys where exclude[key] == true are not written.

type Opts

type Opts struct {
	// Method is the http verb (constants are copied from net/http to avoid import)
	Method string

	// Headers is a map of http headers to send.
	Headers map[string]string

	// Body is the body request
	Body io.Reader

	// Mode docs https://developer.mozilla.org/en-US/docs/Web/API/Request/mode
	Mode string

	// Credentials docs https://developer.mozilla.org/en-US/docs/Web/API/Request/credentials
	Credentials string

	// Cache docs https://developer.mozilla.org/en-US/docs/Web/API/Request/cache
	Cache string

	// Redirect docs https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
	Redirect string

	// Referrer docs https://developer.mozilla.org/en-US/docs/Web/API/Request/referrer
	Referrer string

	// ReferrerPolicy docs https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
	ReferrerPolicy string

	// Integrity docs https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity
	Integrity string

	// KeepAlive docs https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
	KeepAlive *bool

	// Signal docs https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal
	Signal context.Context
}

Opts are the options you can pass to the fetch call.

type Response

type Response struct {
	Headers    Header
	OK         bool
	Redirected bool
	Status     int
	StatusText string
	Type       string
	URL        string
	Body       []byte
	BodyUsed   bool
}

Response is the response that retursn from the fetch promise.

func Fetch

func Fetch(url string, opts *Opts) (*Response, error)

Fetch uses the JS Fetch API to make requests over WASM.