The WebAssembly.Memory
object is a resizable ArrayBuffer
or SharedArrayBuffer
that holds the raw bytes of memory accessed by a WebAssembly Instance
.
A memory created by JavaScript or in WebAssembly code will be accessible and mutable from both JavaScript and WebAssembly.
Constructor
WebAssembly.Memory()
- Creates a new
Memory
object.
Instance properties
Memory.prototype.buffer
- An accessor property that returns the buffer contained in the memory.
Instance methods
Memory.prototype.grow()
- Increases the size of the memory instance by a specified number of WebAssembly pages (each one is 64KB in size).
Examples
Creating a new Memory object
There are two ways to get a WebAssembly.Memory
object. The first way is to construct it from JavaScript. The following example creates a new WebAssembly Memory instance with an initial size of 10 pages (640KiB), and a maximum size of 100 pages (6.4MiB). Its buffer
property will return an ArrayBuffer
.
var memory = new WebAssembly.Memory({initial:10, maximum:100});
The second way to get a WebAssembly.Memory
object is to have it exported by a WebAssembly module. The following example (see memory.html on GitHub, and view it live also) fetches and instantiates the loaded memory.wasm byte code using the WebAssembly.instantiateStreaming()
method, while importing the memory created in the line above. It then stores some values in that memory, then exports a function and uses it to sum some values.
WebAssembly.instantiateStreaming(fetch('memory.wasm'), { js: { mem: memory } }) .then(obj => { var i32 = new Uint32Array(memory.buffer); for (var i = 0; i < 10; i++) { i32[i] = i; } var sum = obj.instance.exports.accumulate(0, 10); console.log(sum); });
Creating a shared memory
By default, WebAssembly memories are unshared. You can create a shared memory by passing shared: true
in the constructor's initialization object:
let memory = new WebAssembly.Memory({initial:10, maximum:100, shared: true});
This memory's buffer
property will return a SharedArrayBuffer
.
Specifications
Specification |
---|
WebAssembly JavaScript Interface The definition of 'Memory' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Memory | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
Memory() constructor | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
buffer | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
grow | Chrome Full support 57 | Edge Full support 16 | Firefox
Full support
52
| IE No support No | Opera Full support 44 | Safari Full support 11 | WebView Android Full support 57 | Chrome Android Full support 57 | Firefox Android
Full support
52
| Opera Android Full support 43 | Safari iOS Full support 11 | Samsung Internet Android Full support 7.0 | nodejs Full support 8.0.0 |
Legend
- Full support
- Full support
- No support
- No support
- See implementation notes.
- See implementation notes.