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.
Constructor
WebAssembly.Instance()
- Creates a new
Instance
object.
Instance properties
Instance.prototype.exports
- 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. Read-only.
Examples
Synchronously instantiating a WebAssembly module
The WebAssembly.Instance()
constructor function can be called to synchronously instantiate a given WebAssembly.Module
object, for example:
const importObject = { imports: { imported_func: function(arg) { console.log(arg); } } }; fetch('simple.wasm').then(response => response.arrayBuffer() ).then(bytes => { let mod = new WebAssembly.Module(bytes); let instance = new WebAssembly.Instance(mod, importObject); instance.exports.exported_func(); })
The preferred way to get an Instance
is asynchronously, for example using the WebAssembly.instantiateStreaming()
function like this:
const importObject = { imports: { imported_func: function(arg) { console.log(arg); } } }; WebAssembly.instantiateStreaming(fetch('simple.wasm'), importObject) .then(obj => obj.instance.exports.exported_func());
This also demonstrates how the exports
property is used to access exported functions.
Specifications
Specification |
---|
WebAssembly JavaScript Interface The definition of 'Instance' in that specification. |
Browser compatibility
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.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Instance | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
Instance() constructor | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
exports | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
Legend
- Full support
- Full support
- No support
- No support
- See implementation notes.
- See implementation notes.