github.com/goplusjs/gopherjs@v1.2.6-0.20211206034512-f187917453b8/README.md (about) 1 GopherJS - A compiler from Go to JavaScript 2 ------------------------------------------- 3 [](https://github.com/goplusjs/gopherjs/actions?query=workflow%3AGo1.12) 4 [](https://github.com/goplusjs/gopherjs/actions?query=workflow%3AGo1.13) 5 [](https://github.com/goplusjs/gopherjs/actions?query=workflow%3AGo1.14) 6 [](https://github.com/goplusjs/gopherjs/actions?query=workflow%3AGo1.15) 7 [](https://github.com/goplusjs/gopherjs/actions?query=workflow%3AGo1.16) 8 9 ### GopherJS 10 This version of GopherJS is a fork of the <https://github.com/gopherjs/gopherjs> 11 12 Supported Go version 13 Go1.12 Go1.13 Go1.14 Go1.15 Go1.16 14 15 ``` 16 go get -u github.com/goplusjs/gopherjs 17 ``` 18 19 20 ### syscall/js 21 ``` 22 package main 23 24 import ( 25 "syscall/js" 26 ) 27 28 func main() { 29 js.Global().Get("document").Call("write", "Hello world!") 30 } 31 ``` 32 33 ``` 34 $ gopherjs serve 35 ``` 36 37 38 *** 39 40 41 [](https://godoc.org/github.com/gopherjs/gopherjs/js) 42 [](https://sourcegraph.com/github.com/gopherjs/gopherjs?badge) 43 44 GopherJS compiles Go code ([golang.org](https://golang.org/)) to pure JavaScript code. Its main purpose is to give you the opportunity to write front-end code in Go which will still run in all browsers. 45 46 ### Playground 47 Give GopherJS a try on the [GopherJS Playground](http://gopherjs.github.io/playground/). 48 49 ### What is supported? 50 Nearly everything, including Goroutines ([compatibility table](https://github.com/gopherjs/gopherjs/blob/master/doc/packages.md)). Performance is quite good in most cases, see [HTML5 game engine benchmark](https://ajhager.github.io/engi/demos/botmark.html). Cgo is not supported. 51 52 ### Installation and Usage 53 Get or update GopherJS and dependencies with: 54 55 ``` 56 go get -u github.com/gopherjs/gopherjs 57 ``` 58 59 Now you can use `gopherjs build [package]`, `gopherjs build [files]` or `gopherjs install [package]` which behave similar to the `go` tool. For `main` packages, these commands create a `.js` file and `.js.map` source map in the current directory or in `$GOPATH/bin`. The generated JavaScript file can be used as usual in a website. Use `gopherjs help [command]` to get a list of possible command line flags, e.g. for minification and automatically watching for changes. 60 61 `gopherjs` uses your platform's default `GOOS` value when generating code. Supported `GOOS` values are: `linux`, `darwin`. If you're on a different platform (e.g., Windows or FreeBSD), you'll need to set the `GOOS` environment variable to a supported value. For example, `GOOS=linux gopherjs build [package]`. 62 63 *Note: GopherJS will try to write compiled object files of the core packages to your $GOROOT/pkg directory. If that fails, it will fall back to $GOPATH/pkg.* 64 65 #### gopherjs run, gopherjs test 66 67 If you want to use `gopherjs run` or `gopherjs test` to run the generated code locally, install Node.js 10.0.0 (or newer), and the `source-map-support` module: 68 69 ``` 70 npm install --global source-map-support 71 ``` 72 73 On supported `GOOS` platforms, it's possible to make system calls (file system access, etc.) available. See [doc/syscalls.md](https://github.com/gopherjs/gopherjs/blob/master/doc/syscalls.md) for instructions on how to do so. 74 75 #### gopherjs serve 76 77 `gopherjs serve` is a useful command you can use during development. It will start an HTTP server serving on ":8080" by default, then dynamically compile your Go packages with GopherJS and serve them. 78 79 For example, navigating to `http://localhost:8080/example.com/user/project/` should compile and run the Go package `example.com/user/project`. The generated JavaScript output will be served at `http://localhost:8080/example.com/user/project/project.js` (the .js file name will be equal to the base directory name). If the directory contains `index.html` it will be served, otherwise a minimal `index.html` that includes `<script src="project.js"></script>` will be provided, causing the JavaScript to be executed. All other static files will be served too. 80 81 Refreshing in the browser will rebuild the served files if needed. Compilation errors will be displayed in terminal, and in browser console. Additionally, it will serve $GOROOT and $GOPATH for sourcemaps. 82 83 If you include an argument, it will be the root from which everything is served. For example, if you run `gopherjs serve github.com/user/project` then the generated JavaScript for the package github.com/user/project/mypkg will be served at http://localhost:8080/mypkg/mypkg.js. 84 85 ### Performance Tips 86 87 - Use the `-m` command line flag to generate minified code. 88 - Apply gzip compression (https://en.wikipedia.org/wiki/HTTP_compression). 89 - Use `int` instead of `(u)int8/16/32/64`. 90 - Use `float64` instead of `float32`. 91 92 ### Community 93 - [#gopherjs Channel on Gophers Slack](https://gophers.slack.com/messages/gopherjs/) (invites to Gophers Slack are available [here](http://blog.gopheracademy.com/gophers-slack-community/#how-can-i-be-invited-to-join:2facdc921b2310f18cb851c36fa92369)) 94 - [Bindings to JavaScript APIs and libraries](https://github.com/gopherjs/gopherjs/wiki/bindings) 95 - [GopherJS Blog](https://medium.com/gopherjs) 96 - [GopherJS on Twitter](https://twitter.com/GopherJS) 97 98 ### Getting started 99 100 #### Interacting with the DOM 101 The package `github.com/gopherjs/gopherjs/js` (see [documentation](https://godoc.org/github.com/gopherjs/gopherjs/js)) provides functions for interacting with native JavaScript APIs. For example the line 102 103 ```js 104 document.write("Hello world!"); 105 ``` 106 107 would look like this in Go: 108 109 ```go 110 js.Global.Get("document").Call("write", "Hello world!") 111 ``` 112 113 You may also want use the [DOM bindings](http://dominik.honnef.co/go/js/dom), the [jQuery bindings](https://github.com/gopherjs/jquery) (see [TodoMVC Example](https://github.com/gopherjs/todomvc)) or the [AngularJS bindings](https://github.com/wvell/go-angularjs). Those are some of the [bindings to JavaScript APIs and libraries](https://github.com/gopherjs/gopherjs/wiki/bindings) by community members. 114 115 #### Providing library functions for use in other JavaScript code 116 Set a global variable to a map that contains the functions: 117 118 ```go 119 package main 120 121 import "github.com/gopherjs/gopherjs/js" 122 123 func main() { 124 js.Global.Set("pet", map[string]interface{}{ 125 "New": New, 126 }) 127 } 128 129 type Pet struct { 130 name string 131 } 132 133 func New(name string) *js.Object { 134 return js.MakeWrapper(&Pet{name}) 135 } 136 137 func (p *Pet) Name() string { 138 return p.name 139 } 140 141 func (p *Pet) SetName(name string) { 142 p.name = name 143 } 144 ``` 145 146 For more details see [Jason Stone's blog post](http://legacytotheedge.blogspot.de/2014/03/gopherjs-go-to-javascript-transpiler.html) about GopherJS. 147 148 ### Architecture 149 150 #### General 151 GopherJS emulates a 32-bit environment. This means that `int`, `uint` and `uintptr` have a precision of 32 bits. However, the explicit 64-bit integer types `int64` and `uint64` are supported. The `GOARCH` value of GopherJS is "js". You may use it as a build constraint: `// +build js`. 152 153 #### Application Lifecycle 154 155 The `main` function is executed as usual after all `init` functions have run. JavaScript callbacks can also invoke Go functions, even after the `main` function has exited. Therefore the end of the `main` function should not be regarded as the end of the application and does not end the execution of other goroutines. 156 157 In the browser, calling `os.Exit` (e.g. indirectly by `log.Fatal`) also does not terminate the execution of the program. For convenience, it calls `runtime.Goexit` to immediately terminate the calling goroutine. 158 159 #### Goroutines 160 Goroutines are fully supported by GopherJS. The only restriction is that you need to start a new goroutine if you want to use blocking code called from external JavaScript: 161 162 ```go 163 js.Global.Get("myButton").Call("addEventListener", "click", func() { 164 go func() { 165 [...] 166 someBlockingFunction() 167 [...] 168 }() 169 }) 170 ``` 171 172 How it works: 173 174 JavaScript has no concept of concurrency (except web workers, but those are too strictly separated to be used for goroutines). Because of that, instructions in JavaScript are never blocking. A blocking call would effectively freeze the responsiveness of your web page, so calls with callback arguments are used instead. 175 176 GopherJS does some heavy lifting to work around this restriction: Whenever an instruction is blocking (e.g. communicating with a channel that isn't ready), the whole stack will unwind (= all functions return) and the goroutine will be put to sleep. Then another goroutine which is ready to resume gets picked and its stack with all local variables will be restored. 177 178 ### GopherJS Development 179 If you're looking to make changes to the GopherJS compiler, see [Developer Guidelines](https://github.com/gopherjs/gopherjs/wiki/Developer-Guidelines) for additional developer information.