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.

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	57	15^[2]	52 (52)^[1]	No support	44	11

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	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.

Examples

Specifications

Browser compatibility

See also

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