WebAssembly.compile()

BaselineWidely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since October 2017.

* Some parts of this feature may have varying levels of support.

TheWebAssembly.compile() static method compiles WebAssembly binary code into aWebAssembly.Module object.This function is useful if it is necessary to compile a module before it can be instantiated (otherwise, theWebAssembly.instantiate() function should be used).

Note:Webpages that have strictContent Security Policy (CSP) might block WebAssembly from compiling and executing modules.For more information on allowing WebAssembly compilation and execution, see thescript-src CSP.

Syntax

WebAssembly.compile(bufferSource)WebAssembly.compile(bufferSource, compileOptions)

Parameters

bufferSource

Atyped array orArrayBuffercontaining the binary code of the Wasm module you want to compile.

compileOptionsOptional

An object containing compilation options. Properties can include:

builtinsOptional: An array of one or more strings that enables the usage ofJavaScript builtins in the compiled Wasm module. The strings define the builtins you want to enable. Currently the only available value is"js-string", which enables JavaScript string builtins.
importedStringConstantsOptional: A string specifying a namespace forimported global string constants. This property needs to be specified if you wish to use imported global string constants in the Wasm module.

Return value

APromise that resolves to aWebAssembly.Module objectrepresenting the compiled module.

Exceptions

IfbufferSource is not atyped array orArrayBuffer,the promise rejects with aTypeError.
If compilation fails, the promise rejects with aWebAssembly.CompileError.

Examples

Using compile

The following example compiles the loaded simple.wasm byte code using thecompile() function and then sends it to aworker usingpostMessage().

const worker = new Worker("wasm_worker.js");fetch("simple.wasm")  .then((response) => response.arrayBuffer())  .then((bytes) => WebAssembly.compile(bytes))  .then((mod) => worker.postMessage(mod));

Note:You'll probably want to useWebAssembly.compileStreaming() in most cases, as it is more efficientthancompile().

Enabling JavaScript builtins and global string imports

This example enables JavaScript string builtins and imported global string constants when compiling the Wasm module withcompile(), before instantiating it withinstantiate() then running the exportedmain() function (which logs"hello world!" to the console).See it running live.

const importObject = {  // Regular import  m: {    log: console.log,  },};const compileOptions = {  builtins: ["js-string"], // Enable JavaScript string builtins  importedStringConstants: "string_constants", // Enable imported global string constants};fetch("log-concat.wasm")  .then((response) => response.arrayBuffer())  .then((bytes) => WebAssembly.compile(bytes, compileOptions))  .then((module) => WebAssembly.instantiate(module, importObject))  .then((instance) => instance.exports.main());