WebAssemblyinstantiate

WebAssembly.instantiate is a JavaScript API used to compile and instantiate WebAssembly modules at runtime. It can take binary data or an already compiled module and returns a Promise that resolves to an object containing both the module and the instance. The instance exposes the module’s exports, which can be called from JavaScript.

Overloads and return shape: The function accepts either a bufferSource (ArrayBuffer or TypedArray) with an optional importObject, or a precompiled WebAssembly.Module with an importObject. In either case, the Promise resolves to an object with properties module (WebAssembly.Module) and instance (WebAssembly.Instance). There is also a synchronous variant, WebAssembly.instantiateSync(module, importObject), which returns a WebAssembly.Instance directly when the module is already compiled.

Streaming and performance: WebAssembly.instantiateStreaming(fetch('module.wasm'), importObject) fetches a WebAssembly binary and compiles it as it downloads, speeding startup for large modules. It returns a Promise that resolves to { module, instance } once ready. This form requires the server to serve the correct MIME type (application/wasm). If fetch is not suitable, WebAssembly.instantiate can also be used with a completed buffer.

Imports and exports: The importObject supplies values for the module’s imports, such as functions, memories, and tables. The instantiated instance exports (instance.exports) provide the functions and other exported entities defined by the module, enabling interaction between WebAssembly code and JavaScript or host environments.

Usage considerations: WebAssembly.instantiate is supported in modern browsers and Node.js. Robust error handling is important for compilation failures or missing imports. For applications prioritizing startup time, instantiateStreaming offers advantages, while instantiateSync can be convenient for synchronous initialization.