Int32Array - JavaScript 编辑

The Int32Array() typed array constructor creates an array of twos-complement 32-bit signed integers in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).

Syntax

new Int32Array(); // new in ES2017
new Int32Array(length);
new Int32Array(typedArray);
new Int32Array(object);
new Int32Array(buffer [, byteOffset [, length]]);

Parameters

length

When called with a length argument, an internal array buffer is created in memory, of size length multiplied by BYTES_PER_ELEMENT bytes, containing zeros.

typedArray

When called with a typedArray argument, which can be an object of any of the typed array types (such as Int32Array), the typedArray gets copied into a new typed array. Each value in typedArray is converted to the corresponding type of the constructor before being copied into the new array. The length of the new typed array will be same as the length of the typedArray argument.

object

When called with an object argument, a new typed array is created as if by the TypedArray.from() method.

buffer, byteOffset, length

When called with a buffer, and optionally a byteOffset and a length argument, a new typed array view is created that views the specified ArrayBuffer. The byteOffset and length parameters specify the memory range that will be exposed by the typed array view. If both are omitted, all of buffer is viewed; if only length is omitted, the remainder of buffer is viewed.

Examples

Different ways to create an Int32Array

// From a length
var int32 = new Int32Array(2);
int32[0] = 42;
console.log(int32[0]); // 42
console.log(int32.length); // 2
console.log(int32.BYTES_PER_ELEMENT); // 4

// From an array
var arr = new Int32Array([21,31]);
console.log(arr[1]); // 31

// From another TypedArray
var x = new Int32Array([21, 31]);
var y = new Int32Array(x);
console.log(y[0]); // 21

// From an ArrayBuffer
var buffer = new ArrayBuffer(16);
var z = new Int32Array(buffer, 0, 4);

// From an iterable
var iterable = function*(){ yield* [1,2,3]; }();
var int32 = new Int32Array(iterable);
// Int32Array[1, 2, 3]

Specifications

Browser compatibility

BCD tables only load in the browser

Compatibility notes

Starting with ECMAScript 2015, Int32Array constructors require to be constructed with a new operator. Calling a Int32Array constructor as a function without new, will throw a TypeError from now on.

var dv = Int32Array([1, 2, 3]);
// TypeError: calling a builtin Int32Array constructor
// without new is forbidden

var dv = new Int32Array([1, 2, 3]);

See also

• JavaScript typed arrays
• ArrayBuffer
• DataView