JavaScript Float64Array : ArrayBufferView

constructor iterable

Float64Array is similar to an Array where each item is a 64 bit (8 byte) floating point number (the same as the standard Number type). Float64Arrays cannot change size after creation.

Spec

Constructors

new Float64Array(length : Number) : Float64Array

Creates a new Float64Array of the specified length where each item starts out as 0.

Example:

var x = new Float64Array(2);
x[0] = 17;
console.log(x[0]);
console.log(x[1]);
console.log(x.length);

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new Float64Array(array : Array) : Float64Array

Creates a new Float64Array and copies the items of array into this.

Example:

var x = new Float64Array([17, -45.3]);
console.log(x[0]);
console.log(x[1]);
console.log(x.length);

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new Float64Array(array : Float64Array) : Float64Array

Creates a new Float64Array and copies the items of array into this. array can be any of the typed array types and the copied items will be converted to 64 bit floating point numbers before being stored in this.

Example:

var x = new Float64Array([17, -45.3]);
var y = new Float64Array(x);
console.log(x[0]);
console.log(x[1]);
console.log(x.length);
x[0] = -2;
console.log(y[0]); // y is not modified

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new Float64Array(buffer : ArrayBuffer, [byteOffset = 0 : Number, [length : Number]]) : Float64Array

Creates a view on top of the specified buffer starting at byteOffset of length items. Changes to the items in this actual affect the underlying buffer, and vice versa. byteOffset must be a multiple of 8. (Use DataView for unaligned data.) If length is not specified, buffer.length - byteOffset must be a multiple of 8 and this.length will be (buffer.length - byteOffset) / 8.

Example:

var buffer = new ArrayBuffer(16);
var x = new Float64Array(buffer, 0, 2);
// Make another view of last 4 bytes of the buffer
var y = new Float64Array(buffer, 8, 1);
x[1] = 7;
console.log(y[0]); // y is a live view on the buffer

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Instance Indexers

this[index : Number] : Number

Gets and sets the element in this at index. index should be between 0 and this.length - 1.

Example:

var x = new Float64Array(2);
x[0] = 17;
console.log(x[0]);
console.log(x[1]);

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Instance Properties

buffer : ArrayBuffer readonly

Returns the underlying buffer for this Float64Array.

Example:

var buffer = new ArrayBuffer(16);
var x = new Float64Array(buffer, 0, 2);
var y = new Float64Array(buffer, 8, 1);
console.log(x.buffer === y.buffer);

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byteLength : Number readonly

The length of this in bytes.

Example:

var buffer = new ArrayBuffer(16);
var x = new Float64Array(buffer, 8, 1);
console.log(x.byteLength); 
console.log(x.length * Float64Array.BYTES_PER_ELEMENT);

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byteOffset : Number readonly

The offset into this.buffer where the 0th item is stored.

Example:

var buffer = new ArrayBuffer(16);
var x = new Float64Array(buffer, 8, 1);
console.log(x.byteOffset);

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length : Number readonly

The number of elements in this. It is 1 greater than the index of the last item.

Example:

var x = new Float64Array(10);
console.log(x.length);

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Instance Methods

copyWithin(target : Number, start : Number, [end : Number]) : undefined

Copies this[start], this[start + 1], ... this[end - 1] to this[target], this[target + 1], ... If end is not specified, this.length is used.

Example:

var x = new Float64Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
x.copyWithin(0, 5);
console.log(x);

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Spec

entries() : Iterator<Array<Number>>

Returns an iterator of the index and items in this where the values of the iterator are of the form [index : Number, item : Number]. See also values() and keys().

Example:

var x = new Float64Array([8, 9]);

// Use for (... of ...) to loop over the iterator
for (var entry of x.entries()) {
  console.dir(entry);
}

// Or access the iterator manually
var entries = x.entries();

console.dir(entries.next());
console.dir(entries.next());
console.dir(entries.next());

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Spec

every(callback : Function, [thisArg : Object]) : Boolean

callback(item : Number, index : Number, array : Float64Array) : Boolean

Returns true if callback returns true for every item in this. Otherwise returns false. The Float64Array passed to callback is the this of the call to every.

Example:

var isEven = function(x) { return (x % 2) === 0; }
console.log(new Float64Array([2, 22, 36]).every(isEven));
console.log(new Float64Array([6, 19, 18]).every(isEven));
console.log(new Float64Array([5, 19, 17]).every(isEven));

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Spec

fill(value : Number, [start = 0 : Number, [end : Number]]) : Float64Array

Fills this[start], this[start + 1], ... this[end - 1] with value. If end is not specified, this.length is used. Returns this.

Example:

var x = new Float64Array(5);

console.log(x.fill(7));
console.log(x.fill(-7, 3));
console.log(x.fill(9, 0, 2));

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Spec

filter(callback : Function, [thisArg : Object]) : Float64Array

callback(item : Number, index : Number, array : Float64Array) : Boolean

Returns a new Float64Array containing only the items in this that callback returned true for. The Float64Array passed to callback is the this of the call to filter.

Example:

var isEven = function(x) { return (x % 2) === 0; }
var numbers = new Float64Array([1, 2, 4, 5, 7, 9, 12]);
console.log(numbers.filter(isEven));

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Spec

find(callback : Function, [thisArg : Object]) : Number

callback(item : Number, index : Number, array : Float64Array) : Boolean

Returns the first item in this where callback returns true for that item. The Float64Array passed to callback is the this of the call to find. See also findIndex().

Example:

var x = new Float64Array([0, -1, -2, -3, -4]);

console.log(x.find(function(item) {
  return item < -3;
}));

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Spec

findIndex(callback : Function, [thisArg : Object]) : Number

callback(item : Number, index : Number, array : Float64Array) : Boolean

Returns the index of the first item in this where callback returns true for that item. The Float64Array passed to callback is the this of the call to find. See also find().

Example:

var x = new Float64Array([0, -1, -2, -3, -4]);

console.log(x.findIndex(function(item) {
  return item < -3;
}));

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Spec

forEach(callback : Function, [thisArg : Object]) : undefined

callback(item : Number, index : Number, array : Float64Array) : undefined

Calls callback for each item in this. The Float64Array passed to callback is the this of the call to forEach.

Example:

var x = new Float64Array([7, 8, 9]);
x.forEach(function(item, index) {
  console.log('item at ' + index + ' = ' + item);
});

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Spec

includes(item : Number, [startingIndex = 0 : Number]) : Boolean

Returns true if item is an element of this starting the search from startingIndex. If startingIndex is negative, this.length is added to it before starting the search.

Example:

var x = new Float64Array([5, 6, 7, 8, 9]);
console.log(x.includes(7));
console.log(x.includes(6, 2));
console.log(x.includes(8, -2));
console.log(x.includes(10));

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Spec

indexOf(item : Number, [startingIndex = 0 : Number]) : Number

Returns the first location of item in this starting the search from start. If startingIndex is negative, this.length is added to it before starting the search. Returns -1 if item is not found. See also lastIndexOf().

Example:

var x = new Float64Array([5, 6, 7, 8, 9, 5, 6]);
console.log(x.indexOf(6));
console.log(x.indexOf(6, 2));
console.log(x.indexOf(5, -2));
console.log(x.indexOf(10, 2));

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Spec

join([separator = ',' : String]) : String

Returns a String created by joining the toString() of each item of this separated by separator.

Example:

var x = new Float64Array([7, 8, 9]);
console.log(x.join());
console.log(x.join(' -- '));

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Spec

keys() : Iterator<Number>

Returns an iterator of the indicies in this. See also entries() and values().

Example:

var x = new Float64Array([8, 9]);

// Use for (... of ...) to loop over the iterator
for (var key of x.keys()) {
  console.dir(key);
}

// Or access the iterator manually
var keys = x.keys();

console.dir(keys.next());
console.dir(keys.next());
console.dir(keys.next());

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Spec

lastIndexOf(item : Number, [startingIndex : Number]) : Number

Returns the location of item by searchig backwards through this, starting the search from startingIndex. If startingIndex is not specified, the search starts from the end of the array. If startingIndex is negative, this.length is added to it before starting the search. Returns -1 if item is not found. See also indexOf().

Example:

var x = new Float64Array([5, 6, 7, 8, 9, 5, 6]);
console.log(x.lastIndexOf(6));
console.log(x.lastIndexOf(6, 2));
console.log(x.lastIndexOf(5, -3));
console.log(x.lastIndexOf(10, 2));

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Spec

map(callback : Function, [thisArg : Object]) : Array

callback(item : Number, index : Number, array : Float64Array) : Object

Returns a new Float64Array with where each item is the result of calling callback on each item in this. The Float64Array passed to callback is the this of the call to map.

Example:

var numbers = new Float64Array([1, 2, 3, 4]);
var squares = numbers.map(function(x) { return x * x; });
console.log(squares);
console.log(numbers);

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Spec

reduce(callback : Function, [initialValue : Object]) : Object

callback(previous : Object, current : Number, index : Number, array : Float64Array) : Object

Calls callback for each item in this in ascending order (0 to length-1). It passes the return value of callback for the i-1th item as the previous parameter for the ith item. Returns the result from the last call to callback. If initialValue is not specified, callback will first be called on this[1] with previous set to this[0]. The Float64Array passed to callback is the this of the call to reduce.

Example:

var x = new Float64Array([0, 1, 2, 3, 4]);
var sum = function(prev, cur) { return prev + cur; } 
console.log(x.reduce(sum));

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Spec

reduceRight(callback : Function, [initialValue : Object]) : Object

callback(previous : Object, current : Number, index : Number, array : Float64Array) : Object

Calls callback for each item in this in descending order (length-1 to 0). It passes the return value of callback for the i+1th item as the previous parameter for the ith item. Returns the result from the last call to callback. If initialValue is not specified, callback will first be called on this[this.length - 2] with previous set to this[this.length - 1]. The Float64Array passed to callback is the this of the call to reduceRight.

Example:

var x = new Float64Array([2, 3]);
var pow = function(prev, cur) { return prev ** cur; } 
console.log(x.reduce(pow)); // 2 ** 3
console.log(x.reduceRight(pow)); // 3 ** 2

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Spec

reverse() : Float64Array

Reverses the order of the items in this and returns this.

Example:

var x = new  Float64Array([1, 2, 3]);
console.log(x.reverse());
console.log(x);

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Spec

set 2 variants

set(array : Array, [offset = 0 : Number]) : undefined

Copies items from array into this starting at this[offset]. Copied items are converted to 64 bit floating point numbers before storing in this.

Example:

var x = new Float64Array(10);
x.set([18, 93, 42], 3);
console.log(x[3]);
console.log(x[4]);
console.log(x[5]);

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set(array : Float64Array, [offset = 0 : Number]) : undefined

Copies items from array into this starting at this[offset]. array can be any of the typed array types and the copied items will be converted to 64 bit floating point numbers before storing in this.

Example:

var x = new Float64Array(10);
x.set(new Float64Array([18, 93, 42]), 3);
console.log(x[3]);
console.log(x[4]);
console.log(x[5]);

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slice(start : Number, [end : Number]) : Float64Array

Returns a new Float64Array which is composed of the items this[start], this[start + 1], ..., this[end - 1]. Note that item[end] is not included. If start or end is negative, the value is added to this.length before performing the slice. If end is not specified, this.length is used.

Example:

var x = new Float64Array([0, 1, 2, 3, 4, 5, 6]);
console.log(x.slice(2));
console.log(x.slice(2, 3));
console.log(x.slice(1, -2));
console.log(x.slice(-4, -1));
console.log(x);

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Spec

some(callback : Function, [thisArg : Object]) : Boolean

callback(item : Number, index : Number, array : Float64Array) : Boolean

Returns true if callback returns true for at least one item in this. Otherwise returns false. The Float64Array passed to callback is the this of the call to some.

Example:

var isEven = function(x) { return (x % 2) === 0; }
console.log(new Float64Array([2, 22, 36]).some(isEven));
console.log(new Float64Array([6, 19, 18]).some(isEven));
console.log(new Float64Array([5, 19, 17]).some(isEven));

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Spec

sort([comparisonFunction : Function]) : Float64Array

comparisonFunction(x : Number, y : Number) : Number

Sort the items of this using comparisonFunction to determine the sort order and returns this. The Number returned by comparisonFunction should be 0 if x and y are equal, negative if x is less than y, or positive if x is greater than y. If comparisonFunction is not specified, the items will be sorted in numeric order. Returns this.

Example:

var x = new Float64Array([52, 7, -14, 22, -9]);

console.log(x.sort());

// Sort by absolute value 
var absComparison = function(x, y) { 
  return Math.abs(x) - Math.abs(y);
};
console.log(x.sort(absComparison));

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Spec

subarray(begin : Number, [end : Number]) : Float64Array

Returns a new Float64Array that is a view on top of this containing items this[begin], this[begin + 1], ..., this[end - 1]. The 0th item in the returned array in the same memory location as this[begin]. If end is not specified, this.length is used.

Example:

var x = new Float64Array([0, 1, 2, 3, 4, 5]); // length=6
var y = x.subarray(2, 5);
console.log(y.length);
console.log(y[0]);
console.log(y[1]);
y[0] = -1;
console.log(x[2]);

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values() : Iterator<Number>

Returns an iterator of the items in this. The values function is also returned for this[Symbol.iterator] so you can iterate over this directly to get the values. See also entries() and keys().

Example:

var x = new Float64Array([8, 9]);

// values is returned by x[Symbol.iterator] so you can just 
// use x directly in the for (... of ...) loop
for (var value of x) {
  console.dir(value);
}

// You can iterate over values explicitly
for (var value of x.values()) {
  console.dir(value);
}

// Or access the iterator manually
var values = x.values();

console.dir(values.next());
console.dir(values.next());
console.dir(values.next());

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Spec

Float64Array Properties

BYTES_PER_ELEMENT : Number

Returns the size in bytes of an item in a Float64Array.

Example:

console.log(Float64Array.BYTES_PER_ELEMENT);

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