This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The WebAssembly.instantiateStreaming()
function compiles and instantiates a WebAssembly module directly from a streamed underlying source.
Syntax
Promise<ResultObject> WebAssembly.instantiateStreaming(source, importObject);
Parameters
- source
- A
Response
object or a promise that will fulfill with one, representing the underlying source of a .wasm module you want to stream, compile, and instantiate. - 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 of the compiled module or else a WebAssembly.LinkError is thrown.
Return value
A Promise
that resolves to a ResultObject
which contains two fields:
module
: AWebAssembly.Module
object representing the compiled WebAssembly module. ThisModule
can be instantiated again, shared via postMessage() or cached in IndexedDB.instance
: AWebAssembly.Instance
object that contains all the Exported WebAssembly functions.
Exceptions
- If either of the parameters are not of the correct type or structure, a
TypeError
is thrown. - If the operation fails, the promise rejects with a
WebAssembly.CompileError
,WebAssembly.LinkError
, orWebAssembly.RuntimeError
, depending on the cause of the failure.
Examples
The following example (see our instantiate-streaming.html demo on GitHub, and view it live also) directly streams a .wasm module from an underlying source then compiles and instantiates it, the promise fulfilling with a ResultObject
. Because the instantiateStreaming()
function accepts a promise for a Response
object, you can directly pass it a WindowOrWorkerGlobalScope.fetch()
call, and it will pass the response into the function when it fulfills.
var importObject = { imports: { imported_func: arg => console.log(arg) } }; WebAssembly.instantiateStreaming(fetch('simple.wasm'), importObject) .then(obj => obj.instance.exports.exported_func());
The ResultObject
's instance member is then accessed, and the contained exported function invoked.
Specifications
Specification | Status | Comment |
---|---|---|
WebAssembly features for web embedding The definition of 'instantiateStreaming()' in that specification. |
Draft | Initial draft definition. |
Browser compatibility
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 61 | No | 58 | No | 47 | ? |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | 61 | 61 | No | 58 | No | ? | ? |