WebAssembly.compile()
Baseline Widely 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.
The WebAssembly.compile() static method compiles WebAssembly binary code into a WebAssembly.Module object. This function is useful if it is necessary to compile a module before it can be instantiated (otherwise, the WebAssembly.instantiate() function should be used).
Note: Webpages that have strict Content Security Policy (CSP) might block WebAssembly from compiling and executing modules. For more information on allowing WebAssembly compilation and execution, see the script-src CSP.
Syntax
WebAssembly.compile(bufferSource) WebAssembly.compile(bufferSource, compileOptions) Parameters
bufferSourceA typed array or
ArrayBuffercontaining the binary code of the Wasm module you want to compile.compileOptionsOptionalAn object containing compilation options. Properties can include:
builtinsOptionalAn array of one or more strings that enables the usage of JavaScript 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.importedStringConstantsOptionalA string specifying a namespace for imported global string constants. This property needs to be specified if you wish to use imported global string constants in the Wasm module.
Return value
A Promise that resolves to a WebAssembly.Module object representing the compiled module.
Exceptions
- If
bufferSourceis not a typed array orArrayBuffer, the promise rejects with aTypeError. - If compilation fails, the promise rejects with a
WebAssembly.CompileError.
Examples
Using compile
The following example compiles the loaded simple.wasm byte code using the compile() function and then sends it to a worker using postMessage().
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 use WebAssembly.compileStreaming() in most cases, as it is more efficient than compile().
Enabling JavaScript builtins and global string imports
This example enables JavaScript string builtins and imported global string constants when compiling the Wasm module with compile(), before instantiating it with instantiate() then running the exported main() 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()); Specifications
| Specification |
|---|
| WebAssembly JavaScript Interface # dom-webassembly-compile |
