值得期待：Go对WebAssmbly的完全支持

WebAssembly获得了所有浏览器的一致支持， Chrome 和 Firefox 已经原生支持 WebAssembly，Edge 和 Safari 也在预览版中加入了 WebAssembly 支持。

Go很快也会对WebAssembly进行支持，目前还处理开发阶段。社区已经有对应的指导文档，下面就是社区的部分指导步骤。
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Compiling Go code to wasm is also doable, but the support for this backend hasn’t been yet integrated into gc. An issue is tracking the progress of this feature: https://github.com/golang/go/issues/18892. As that discussion is quite long, here is the executive summary: a development branch with preliminary support for wasm has been created by @neelance (Richard Musiol) (yeah!).

Here are the instructions to compile a gc toolchain with a GOOS=js GOARCH=wasm environment:

$> cd somewhere
$> git clone https://go.googlesource.com/go
$> cd go
$> git remote add neelance https://github.com/neelance/go
$> git fetch --all
$> git checkout wasm-wip
$> cd src
$> ./make.bash
$> cd ../misc/wasm

The misc/wasm directory contains all the files (save the actual wasm module) to execute a wasm module with nodejs.

Let us compile the following main.go file:

package main

func main() {
    println("Hello World, from wasm+Go")
}

with our new wasm-capable go binary:

$> GOARCH=wasm GOOS=js go build -o test.wasm main.go
$> ll
total 4.0K
-rw-r--r-- 1 binet binet   68 Dec 14 14:30 main.go
-rwxr-xr-x 1 binet binet 947K Dec 14 14:30 test.wasm
Copy over the misc/wasm files under this directory, and then finally, run the following server.go file:

package main

import (
    "flag"
    "log"
    "net/http"
)

func main() {
    addr := flag.String("addr", ":5555", "server address:port")
    flag.Parse()
    srv := http.FileServer(http.Dir("."))
    log.Printf("listening on %q...", *addr)
    log.Fatal(http.ListenAndServe(*addr, srv))
}

Like so:

$> ll
total 968K
-rw-r--r-- 1 binet binet   68 Dec 14 14:30 main.go
-rw-r--r-- 1 binet binet  268 Dec 14 14:38 server.go
-rwxr-xr-x 1 binet binet 947K Dec 14 14:30 test.wasm
-rw-r--r-- 1 binet binet  482 Dec 14 14:32 wasm_exec.html
-rwxr-xr-x 1 binet binet 7.9K Dec 14 14:32 wasm_exec.js

$> go run ./server.go
2017/12/14 14:39:18 listening on ":5555"...

Navigating to localhost:5555/wasm_exec.html will present you with a [Run] button that, when clicked should display “Hello World, from wasm+Go” in the console.

We’ve just had our browser run a wasm module, generated with our favorite compilation toolchain!

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WebAssembly 的出现则提供了一个更好的选择：接近原生的运算效率，开源、兼容性好、平台覆盖广的标准，以及可以借此机会抛弃 JavaScript 的历史遗留问题。

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