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A WebAssembly.Instance object is a stateful, executable instance of a WebAssembly.ModuleInstance objects contain all the Exported WebAssembly functions that allow calling into WebAssembly code from JavaScript.

WebAssembly.Instance实例对象是有状态,可执行的 WebAssembly.Module实例。实例中包含了所有可以被 JavaScript调用的WebAssembly 代码导出的函数。

The WebAssembly.Instance() constructor function can be called to synchronously instantiate a given WebAssembly.Module object. However, the primary way to get an Instance is through the asynchronous WebAssembly.instantiate() function.

Constructor Syntax

Important: Since instantiation for large modules can be expensive, developers should only use the Instance() constructor when synchronous instantiation is absolutely required; the asynchronous WebAssembly.instantiate() method should be used at all other times.

var myInstance = new WebAssembly.Instance(module, importObject);


The WebAssembly.Module object to be instantiated.
importObject 可选
An object containing the values to be imported into the newly-created Instance, such as functions or WebAssembly.Memory objects. There must be one matching property for each declared import of module or else a WebAssembly.LinkError is thrown.

Instance instances

All Instance instances inherit from the Instance() constructor's prototype object — this can be modified to affect all Instance instances.

Instance properties

Returns the function that created this object's instance. By default this is the WebAssembly.Instance() constructor.
Instance.prototype.exports Read only
Returns an object containing as its members all the functions exported from the WebAssembly module instance, to allow them to be accessed and used by JavaScript.

Instance methods



Specification Status Comment
Web Assembly JavaScript API
Draft Initial draft definition.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 57 15[2] 52 (52)[1] 未实现 44 11
Feature Chrome for Android Android Webview Edge Mobile Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 57 57 未实现 52.0 (52)[1] 未实现 未实现 11

[1] WebAssembly is enabled in Firefox 52+, although disabled in the Firefox 52 Extended Support Release (ESR.)

[2] Currently supported behind the “Experimental JavaScript Features” flag. See this blog post for more details.

See also


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