WebAssembly.Global
对象表示一个全局变量实例, 可以被JavaScript 和importable/exportable 访问 ,跨越一个或多个WebAssembly.Module
实例. 他允许被多个modules动态连接.
构造函数语法
var myGlobal = new WebAssembly.Global(descriptor, value);
参数
- descriptor
-
GlobalDescriptor
包含2个属性的表:value
: AUSVString
表示全局变量的数据类型. 可以是i32
,i64
,f32
, 或f64
.mutable
: 布尔值决定是否可以修改. 默认是false
.
- value
-
可以是任意变量值. This can be any value,需要其类型与变量类型匹配. 如果变量没有定义, 使用0代替,参考
DefaultValue
algorithm.
Global 构造函数属性
None.
Global 实例
所有的 Global
实例 继承自 Global()
构造函数 prototype object — 修改会影响 所有 Global
实例.
实例属性
-
Global.prototype.constructor
-
Returns the function that created this object's instance. By default this is the
WebAssembly.Global()
constructor. -
Global.prototype[@@toStringTag]
- The initial value of the @@toStringTag property is the String value "WebAssembly.Global".
-
Global.prototype.value
- The value contained inside the global variable — this can be used to directly set and get the global's value.
实例方法
-
Global.prototype.valueOf()
- Old-style method that returns the value contained inside the global variable.
例子
以下例子展示了使用 WebAssembly.Global()
构造函数创建一个新的实例. 它定义为可修饰的 类型为i32
, 值为 0.
global的值发生改变, 首先设置Global.value
为42, 然后使用导出函数 incGlobal()
增加为43. 导出函数在 global.wasm
模块中(它将参数的值加一并返回).
const output = document.getElementById('output'); function assertEq(msg, got, expected) { output.innerHTML += `Testing ${msg}: `; if (got !== expected) output.innerHTML += `FAIL!<br>Got: ${got}<br>Expected: ${expected}<br>`; else output.innerHTML += `SUCCESS! Got: ${got}<br>`; } assertEq("WebAssembly.Global exists", typeof WebAssembly.Global, "function"); const global = new WebAssembly.Global({value:'i32', mutable:true}, 0); WebAssembly.instantiateStreaming(fetch('global.wasm'), { js: { global } }) .then(({instance}) => { assertEq("getting initial value from wasm", instance.exports.getGlobal(), 0); global.value = 42; assertEq("getting JS-updated value from wasm", instance.exports.getGlobal(), 42); instance.exports.incGlobal(); assertEq("getting wasm-updated value from JS", global.value, 43); });
注意: 你可以在running live on GitHub 查看例子; 也可以访问source code.
规格
规格 | 状态 | 解释 |
---|---|---|
WebAssembly JavaScript Interface WebAssembly.Global() |
Working Draft | Initial draft definition. |
浏览器兼容性
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out
https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Global |
Chrome Full support 69 | Edge No support No | Firefox Full support 62 | IE No support No | Opera No support No | Safari No support No | WebView Android Full support 69 | Chrome Android Full support 69 | Firefox Android Full support 62 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support 10.0 | nodejs No support No |
value |
Chrome Full support 69 | Edge No support No | Firefox Full support 62 | IE No support No | Opera No support No | Safari No support No | WebView Android Full support 69 | Chrome Android Full support 69 | Firefox Android Full support 62 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support 10.0 | nodejs No support No |
valueOf |
Chrome Full support 69 | Edge No support No | Firefox Full support 62 | IE No support No | Opera No support No | Safari No support No | WebView Android Full support 69 | Chrome Android Full support 69 | Firefox Android Full support 62 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support 10.0 | nodejs No support No |
Legend
- Full support
- Full support
- No support
- No support