@stdlib/array/little-endian-factory/README.md

Arrays.

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# littleEndianFactory

> Return a typed array constructor for creating typed arrays stored in little-endian byte order.

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<section class="intro">

In contrast to the built-in typed array constructors which store values according to the host platform byte order, the typed array constructors returned by the factory function always access elements in little-endian byte order. Such enforcement can be particularly advantageous when working with memory buffers which do not necessarily follow host platform byte order, such as [WebAssembly memory][@stdlib/wasm/memory].

</section>

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<section class="usage">

## Usage

```javascript
var littleEndianFactory = require( '@stdlib/array/little-endian-factory' );
```

#### littleEndianFactory( dtype )

Returns a typed array constructor for creating typed arrays having a specified [data type][@stdlib/array/typed-dtypes] and stored in little-endian byte order.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );
// returns <Function>

var Float32ArrayLE = littleEndianFactory( 'float32' );
// returns <Function>
```

* * *

### Typed Array Constructor

#### TypedArrayLE()

A typed array constructor which returns a typed array representing an array of values in little-endian byte order.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE();
// returns <Float64ArrayLE>
```

#### TypedArrayLE( length )

Returns a typed array having a specified length.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
// returns <Float64ArrayLE>
```

#### TypedArrayLE( typedarray )

Creates a typed array from another typed array.

```javascript
var Float32Array = require( '@stdlib/array/float32' );

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr1 = new Float32Array( [ 0.5, 0.5, 0.5 ] );
var arr2 = new Float64ArrayLE( arr1 );
// returns <Float64ArrayLE>

var v = arr2.get( 0 );
// returns 0.5
```

#### TypedArrayLE( obj )

Creates a typed array from an array-like object or iterable.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 0.5, 0.5, 0.5 ] );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 0.5
```

#### TypedArrayLE( buffer\[, byteOffset\[, length]] )

Returns a typed array view of an [`ArrayBuffer`][@stdlib/array/buffer].

```javascript
var ArrayBuffer = require( '@stdlib/array/buffer' );

var Float64ArrayLE = littleEndianFactory( 'float64' );

var buf = new ArrayBuffer( 32 );
var arr = new Float64ArrayLE( buf, 0, 4 );
// returns <Float64ArrayLE>
```

* * *

### Typed Array Properties

<a name="static-prop-bytes-per-element"></a>

#### TypedArrayLE.BYTES_PER_ELEMENT

Number of bytes per view element.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var nbytes = Float64ArrayLE.BYTES_PER_ELEMENT;
// returns 8
```

<a name="static-prop-name"></a>

#### TypedArrayLE.name

Typed array constructor name.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var str = Float64ArrayLE.name;
// returns 'Float64ArrayLE'
```

<a name="prop-buffer"></a>

#### TypedArrayLE.prototype.buffer

**Read-only** property which returns the [`ArrayBuffer`][@stdlib/array/buffer] referenced by the typed array.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var buf = arr.buffer;
// returns <ArrayBuffer>
```

<a name="prop-byte-length"></a>

#### TypedArrayLE.prototype.byteLength

**Read-only** property which returns the length (in bytes) of the typed array.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var byteLength = arr.byteLength;
// returns 40
```

<a name="prop-byte-offset"></a>

#### TypedArrayLE.prototype.byteOffset

**Read-only** property which returns the offset (in bytes) of the typed array from the start of its [`ArrayBuffer`][@stdlib/array/buffer].

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var byteOffset = arr.byteOffset;
// returns 0
```

<a name="prop-bytes-per-element"></a>

#### TypedArrayLE.prototype.BYTES_PER_ELEMENT

Number of bytes per view element.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var nbytes = arr.BYTES_PER_ELEMENT;
// returns 8
```

<a name="prop-length"></a>

#### TypedArrayLE.prototype.length

**Read-only** property which returns the number of view elements.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 5 );
var len = arr.length;
// returns 5
```

* * *

### Typed Array Methods

<a name="static-method-from"></a>

#### TypedArrayLE.from( src\[, map\[, thisArg]] )

Creates a new typed array from an array-like object or an iterable.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = Float64ArrayLE.from( [ 1.0, -1.0 ] );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 1.0
```

To invoke a function for each `src` value, provide a callback function.

```javascript
function mapFcn( v ) {
    return v * 2.0;
}

var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = Float64ArrayLE.from( [ 1.0, -1.0 ], mapFcn );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 2.0
```

A callback function is provided two arguments:

-   **value**: source value.
-   **index**: source index.

To set the callback execution context, provide a `thisArg`.

```javascript
function mapFcn( v ) {
    this.count += 1;
    return v * 2.0;
}

var Float64ArrayLE = littleEndianFactory( 'float64' );

var ctx = {
    'count': 0
};

var arr = Float64ArrayLE.from( [ 1.0, -1.0 ], mapFcn, ctx );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 2.0

var n = ctx.count;
// returns 2
```

<a name="static-method-of"></a>

#### TypedArrayLE.of( element0\[, element1\[, ...elementN]] )

Creates a new typed array from a variable number of arguments.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = Float64ArrayLE.of( 1.0, -1.0 );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 1.0
```

<a name="method-get"></a>

#### TypedArrayLE.prototype.get( i )

Returns an array element located at a nonnegative integer position (index) `i`.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 10 );

// Set the first element:
arr.set( 1.0, 0 );

// Get the first element:
var v = arr.get( 0 );
// returns 1.0
```

If provided an out-of-bounds index, the method returns `undefined`.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( 10 );

var v = arr.get( 100 );
// returns undefined
```

<a name="method-set"></a>

#### TypedArrayLE.prototype.set( arr\[, offset] )

Sets array elements.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 1.0, 2.0, 3.0 ] );
// returns <Float64ArrayLE>

var v = arr.get( 0 );
// returns 1.0

v = arr.get( 1 );
// returns 2.0

// Set the first two array elements:
arr.set( [ 4.0, 5.0 ] );

v = arr.get( 0 );
// returns 4.0

v = arr.get( 1 );
// returns 5.0
```

By default, the method starts writing values at the first array index. To specify an alternative index, provide an index `offset`.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 1.0, 2.0, 3.0 ] );
// returns <Float64ArrayLE>

// Set the last two array elements:
arr.set( [ 4.0, 5.0 ], 1 );

var v = arr.get( 1 );
// returns 4.0

v = arr.get( 2 );
// returns 5.0
```

A few notes:

-   If `i` is out-of-bounds, the method throws an error.
-   If a target array cannot accommodate all values (i.e., the length of source array plus `i` exceeds the target array length), the method throws an error.
-   If provided a typed array which shares an [`ArrayBuffer`][@stdlib/array/buffer] with the target array, the method will intelligently copy the source range to the destination range.

<a name="method-to-string"></a>

#### TypedArrayLE.prototype.toString()

Serializes an array as a string.

```javascript
var Float64ArrayLE = littleEndianFactory( 'float64' );

var arr = new Float64ArrayLE( [ 1.0, 2.0, 3.0 ] );

var str = arr.toString();
// returns '1,2,3'
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

* * *

## Notes

-   While returned constructors _strive_ to maintain (but do not **guarantee**) consistency with [typed arrays][@stdlib/array/typed], significant deviations from ECMAScript-defined [typed array][@stdlib/array/typed] behavior are as follows:

    -   Constructors **not** require the `new` operator.
    -   Accessing array elements using bracket syntax (e.g., `X[i]`) is **not** supported. Instead, one **must** use the `.get()` method.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

* * *

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var Float64Array = require( '@stdlib/array/float64' );
var logEach = require( '@stdlib/console/log-each' );
var littleEndianFactory = require( '@stdlib/array/little-endian-factory' );

var Float64ArrayLE = littleEndianFactory( 'float64' );

// Create a typed array by specifying a length:
var out = new Float64ArrayLE( 3 );
logEach( '%s', out );

// Create a typed array from an array:
var arr = [ 1.0, -1.0, -3.14, 3.14, 0.5, 0.5 ];
out = new Float64ArrayLE( arr );
logEach( '%s', out );

// Create a typed array from an array buffer:
arr = new Float64Array( [ 1.0, -1.0, -3.14, 3.14, 0.5, 0.5 ] ); // host byte order
out = new Float64ArrayLE( arr.buffer );
logEach( '%s', out );

// Create a typed array from an array buffer view:
arr = new Float64Array( [ 1.0, -1.0, -3.14, 3.14, 0.5, 0.5 ] ); // host byte order
out = new Float64ArrayLE( arr.buffer, 8, 2 );
logEach( '%s', out );
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

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<section class="links">

[@stdlib/array/typed]: https://github.com/stdlib-js/array/tree/main/typed

[@stdlib/array/buffer]: https://github.com/stdlib-js/array/tree/main/buffer

[@stdlib/wasm/memory]: https://www.npmjs.com/package/@stdlib/wasm-memory

[@stdlib/array/typed-dtypes]: https://github.com/stdlib-js/array/tree/main/typed-dtypes

</section>

<!-- /.links -->