Float64Array() constructor

The Float64Array() typed array constructor creates a new Float64Array object, which is, an array of 64-bit floating point numbers (corresponding to the C double data type) 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 Float64Array(); // new in ES2017
new Float64Array(length);
new Float64Array(typedArray);
new Float64Array(object);

new Float64Array(buffer);
new Float64Array(buffer, byteOffset);
new Float64Array(buffer, byteOffset, length);

Description

The Float64Array constructor requires being constructed with a new operator. Calling the Float64Array constructor as a function without new will throw a TypeError.

const dv = Float64Array([1, 2, 3]);
// TypeError: calling a builtin Float64Array constructor
// without new is forbidden

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 non-bigint 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 a Float64Array

// From a length
const float64 = new Float64Array(2);
float64[0] = 42;
console.log(float64[0]); // 42
console.log(float64.length); // 2
console.log(float64.BYTES_PER_ELEMENT); // 8

// From an array
const x = new Float64Array([21, 31]);
console.log(x[1]); // 31

// From another TypedArray
const y = new Float64Array(x);
console.log(y[0]); // 21

// From an ArrayBuffer
const buffer = new ArrayBuffer(64);
const z = new Float64Array(buffer, 8, 4);
console.log(z.byteOffset); // 8

// From an iterable
const iterable = function*() { yield* [1, 2, 3]; }();
const float64FromIterable = new Float64Array(iterable);
console.log(float64FromIterable);
// Float64Array [1, 2, 3]

Specifications

Specification
ECMAScript Language Specification
# sec-typedarray-constructors

Browser compatibility

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See also