WebAssembly.Instance.prototype.exports

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The exports readonly property of the WebAssembly.Instance object prototype 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.exports

Examples

After fetching some WebAssembly bytecode using fetch, we compile and instantiate the module using the WebAssembly.instantiate() function, importing a JavaScript function into the WebAssembly Module in the process. We then call an Exported WebAssembly function that is exported by the Instance.

var importObject = {
  imports: {
    imported_func: function(arg) {
      console.log(arg);
    }
  }
};

fetch('simple.wasm').then(response =>
  response.arrayBuffer()
).then(bytes =>
  WebAssembly.instantiate(bytes, importObject)
).then(result =>
  result.instance.exports.exported_func()
);

Note: See index.html on GitHub (view it live also) for a similar example that makes use of our fetchAndInstantiate() library function.

Specifications

Specification Status Comment
Web Assembly JavaScript API
The definition of 'WebAssembly.Instance objects' in that specification.
Draft Initial draft definition.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 57 No support 52 (52)[1] No support (Yes) No support
Feature Chrome for Android Android Webview Edge Mobile Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 57 57 No support 52.0 (52)[1] No support No support No support

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

See also

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, fscholz
 Last updated by: chrisdavidmills,