A WebAssembly.Instance
object is a stateful, executable instance of a WebAssembly.Module. Instance
objects contain all the Exported WebAssembly functions that allow calling into WebAssembly code from JavaScript.
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);
Parameters
- module
- The
WebAssembly.Module
object to be instantiated. - importObject Optional
- An object containing the values to be imported into the newly-created
Instance
, such as functions orWebAssembly.Memory
objects. There must be one matching property for each declared import ofmodule
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
Instance.prototype.constructor
- 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
None.
Specifications
Specification | Status | Comment |
---|---|---|
WebAssembly JavaScript API The definition of 'Instance' in that specification. |
Draft | Initial draft definition. |
Browser compatibility
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 57 | 16 | 522 | No | 44 | 11 |
exports | 57 | 16 | 522 | No | 44 | 11 |
prototype | 57 | 16 | 522 | No | 44 | 11 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | 57 | 57 | Yes1 | 522 | No | ? | 11 |
exports | 57 | 57 | Yes1 | 522 | No | ? | 11 |
prototype | 57 | 57 | Yes1 | 522 | No | ? | 11 |
1. This feature is behind the Experimental JavaScript Features
preference.
2. Disabled in the Firefox 52 Extended Support Release (ESR).