@stdlib/array-uint8 NPM

Uint8Array

Typed array constructor which returns a typed array representing an array of 8-bit unsigned integers in the platform byte order.

Installation

npm install @stdlib/array-uint8

Usage

var Uint8Array = require( '@stdlib/array-uint8' );

Uint8Array()

A typed array constructor which returns a typed array representing an array of 8-bit unsigned integers in the platform byte order.

var arr = new Uint8Array();
// returns <Uint8Array>

Uint8Array( length )

Returns a typed array having a specified length.

var arr = new Uint8Array( 5 );
// returns <Uint8Array>[ 0, 0, 0, 0, 0 ]

Uint8Array( typedarray )

Creates a typed array from another typed array.

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

var arr1 = new Float32Array( [ 5.0, 5.0, 5.0 ] );
var arr2 = new Uint8Array( arr1 );
// returns <Uint8Array>[ 5, 5, 5 ]

Uint8Array( obj )

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

var arr = new Uint8Array( [ 5.0, 5.0, 5.0 ] );
// returns <Uint8Array>[ 5, 5, 5 ]

Uint8Array( buffer[, byteOffset[, length]] )

Returns a typed array view of an ArrayBuffer.

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

var buf = new ArrayBuffer( 4 );
var arr = new Uint8Array( buf, 0, 4 );
// returns <Uint8Array>[ 0, 0, 0, 0 ]

Properties

Uint8Array.BYTES_PER_ELEMENT

Number of bytes per view element.

var nbytes = Uint8Array.BYTES_PER_ELEMENT;
// returns 1

Uint8Array.name

Typed array constructor name.

var str = Uint8Array.name;
// returns 'Uint8Array'

Uint8Array.prototype.buffer

Read-only property which returns the ArrayBuffer referenced by the typed array.

var arr = new Uint8Array( 5 );
var buf = arr.buffer;
// returns <ArrayBuffer>

Uint8Array.prototype.byteLength

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

var arr = new Uint8Array( 5 );
var byteLength = arr.byteLength;
// returns 5

Uint8Array.prototype.byteOffset

Read-only property which returns the offset (in bytes) of the typed array from the start of its ArrayBuffer.

var arr = new Uint8Array( 5 );
var byteOffset = arr.byteOffset;
// returns 0

Uint8Array.prototype.BYTES_PER_ELEMENT

Number of bytes per view element.

var arr = new Uint8Array( 5 );
var nbytes = arr.BYTES_PER_ELEMENT;
// returns 1

Uint8Array.prototype.length

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

var arr = new Uint8Array( 5 );
var len = arr.length;
// returns 5

Methods

Uint8Array.from( src[, map[, thisArg]] )

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

var arr = Uint8Array.from( [ 1, 2 ] );
// returns <Uint8Array>[ 1, 2 ]

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

function mapFcn( v ) {
    return v * 2;
}

var arr = Uint8Array.from( [ 1, 2 ], mapFcn );
// returns <Uint8Array>[ 2, 4 ]

A callback function is provided two arguments:

value: source value
index: source index

To set the callback execution context, provide a thisArg.

function mapFcn( v ) {
    this.count += 1;
    return v * 2;
}

var ctx = {
    'count': 0
};

var arr = Uint8Array.from( [ 1, 2 ], mapFcn, ctx );
// returns <Uint8Array>[ 2, 4 ]

var n = ctx.count;
// returns 2

Uint8Array.of( element0[, element1[, ...elementN]] )

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

var arr = Uint8Array.of( 1, 2 );
// returns <Uint8Array>[ 1, 2 ]

Uint8Array.prototype.copyWithin( target, start[, end] )

Copies a sequence of elements within an array starting at start and ending at end (non-inclusive) to the position starting at target.

var arr = new Uint8Array( [ 1, 2, 3, 4, 5 ] );

// Copy the last two elements to the first two elements:
arr.copyWithin( 0, 3 );

var v = arr[ 0 ];
// returns 4

v = arr[ 1 ];
// returns 5

By default, end equals the number of array elements (i.e., one more than the last array index). To limit the sequence length, provide an end argument.

var arr = new Uint8Array( [ 1, 2, 3, 4, 5 ] );

// Copy the first two elements to the last two elements:
arr.copyWithin( 3, 0, 2 );

var v = arr[ 3 ];
// returns 1

v = arr[ 4 ];
// returns 2

When a target, start, and/or end index is negative, the respective index is determined relative to the last array element. The following example achieves the same behavior as the previous example:

var arr = new Uint8Array( [ 1, 2, 3, 4, 5 ] );

// Copy the first two elements to the last two elements:
arr.copyWithin( -2, -5, -3 );

var v = arr[ 3 ];
// returns 1

v = arr[ 4 ];
// returns 2

Uint8Array.prototype.entries()

Returns an iterator for iterating over array key-value pairs.

var arr = new Uint8Array( [ 1, 2 ] );

// Create an iterator:
var it = arr.entries();

// Iterate over key-value pairs...
var v = it.next().value;
// returns [ 0, 1 ]

v = it.next().value;
// returns [ 1, 2 ]

var bool = it.next().done;
// returns true

Uint8Array.prototype.every( predicate[, thisArg] )

Tests whether all array elements pass a test implemented by a predicate function.

function predicate( v ) {
    return ( v <= 1 );
}

var arr = new Uint8Array( [ 1, 2 ] );

var bool = arr.every( predicate );
// returns false

A predicate function is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function predicate( v ) {
    this.count += 1;
    return ( v >= 1 );
}

var ctx = {
    'count': 0
};

var arr = new Uint8Array( [ 1, 2 ] );

var bool = arr.every( predicate, ctx );
// returns true

var n = ctx.count;
// returns 2

Uint8Array.prototype.fill( value[, start[, end]] )

Fills an array from a start index to an end index (non-inclusive) with a provided value.

var arr = new Uint8Array( 2 );

// Set all array elements to the same value:
arr.fill( 2 );

var v = arr[ 0 ];
// returns 2

v = arr[ 1 ];
// returns 2

// Set all array elements starting from the first index to the same value:
arr.fill( 3, 1 );

v = arr[ 0 ];
// returns 2

v = arr[ 1 ];
// returns 3

// Set all array elements, except the last element, to the same value:
arr.fill( 4, 0, arr.length-1 );

v = arr[ 0 ];
// returns 4

v = arr[ 1 ];
// returns 3

When a start and/or end index is negative, the respective index is determined relative to the last array element.

var arr = new Uint8Array( 2 );

// Set all array elements, except the last element, to the same value:
arr.fill( 2, -arr.length, -1 );

var v = arr[ 0 ];
// returns 2

v = arr[ 1 ];
// returns 0

Uint8Array.prototype.filter( predicate[, thisArg] )

Creates a new array (of the same data type as the host array) which includes those elements for which a predicate function returns a truthy value.

function predicate( v ) {
    return ( v >= 2 );
}

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.filter( predicate );
// returns <Uint8Array>[ 2, 3 ]

If a predicate function does not return a truthy value for any array element, the method returns an empty array.

function predicate( v ) {
    return ( v >= 10 );
}

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.filter( predicate );
// returns <Uint8Array>[]

A predicate function is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function predicate( v ) {
    this.count += 1;
    return ( v >= 2 );
}

var ctx = {
    'count': 0
};

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.filter( predicate, ctx );

var n = ctx.count;
// returns 3

Uint8Array.prototype.find( predicate[, thisArg] )

Returns the first array element for which a provided predicate function returns a truthy value.

function predicate( v ) {
    return ( v > 2 );
}

var arr = new Uint8Array( [ 1, 2, 3 ] );

var v = arr.find( predicate );
// returns 3

If a predicate function does not return a truthy value for any array element, the method returns undefined.

function predicate( v ) {
    return ( v < 1 );
}

var arr = new Uint8Array( [ 1, 2, 3 ] );

var v = arr.find( predicate );
// returns undefined

A predicate function is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function predicate( v ) {
    this.count += 1;
    return ( v > 2 );
}

var ctx = {
    'count': 0
};

var arr = new Uint8Array( [ 1, 2, 3 ] );

var v = arr.find( predicate, ctx );
// returns 3

var n = ctx.count;
// returns 3

Uint8Array.prototype.findIndex( predicate[, thisArg] )

Returns the index of the first array element for which a provided predicate function returns a truthy value.

function predicate( v ) {
    return ( v >= 3 );
}

var arr = new Uint8Array( [ 1, 2, 3 ] );

var idx = arr.findIndex( predicate );
// returns 2

If a predicate function does not return a truthy value for any array element, the method returns -1.

function predicate( v ) {
    return ( v < 1 );
}

var arr = new Uint8Array( [ 1, 2, 3 ] );

var idx = arr.findIndex( predicate );
// returns -1

A predicate function is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function predicate( v ) {
    this.count += 1;
    return ( v >= 3 );
}

var ctx = {
    'count': 0
};

var arr = new Uint8Array( [ 1, 2, 3 ] );

var idx = arr.findIndex( predicate, ctx );
// returns 2

var n = ctx.count;
// returns 3

Uint8Array.prototype.forEach( fcn[, thisArg] )

Invokes a callback for each array element.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var str = '';

function fcn( v, i ) {
    str += i + ':' + v;
    if ( i < arr.length-1 ) {
        str += ' ';
    }
}

arr.forEach( fcn );

console.log( str );
// => '0:1 1:2 2:3'

The callback is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function fcn() {
    this.count += 1;
}

var ctx = {
    'count': 0
};

var arr = new Uint8Array( [ 1, 2, 3 ] );

arr.forEach( fcn, ctx );

var n = ctx.count;
// returns 3

Uint8Array.prototype.includes( searchElement[, fromIndex] )

Returns a boolean indicating whether an array includes a search element.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var bool = arr.includes( 3 );
// returns true

bool = arr.includes( 0 );
// returns false

By default, the method searches the entire array (fromIndex = 0). To begin searching from a specific array index, provide a fromIndex.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var bool = arr.includes( 1, 1 );
// returns false

When a fromIndex is negative, the starting index is resolved relative to the last array element.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var bool = arr.includes( 1, -2 );
// returns false

Uint8Array.prototype.indexOf( searchElement[, fromIndex] )

Returns the index of the first array element strictly equal to a search element.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var idx = arr.indexOf( 3 );
// returns 2

idx = arr.indexOf( 0 );
// returns -1

By default, the method searches the entire array (fromIndex = 0). To begin searching from a specific array index, provide a fromIndex.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var idx = arr.indexOf( 1, 1 );
// returns -1

When a fromIndex is negative, the starting index is resolved relative to the last array element.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var idx = arr.indexOf( 1, -2 );
// returns -1

Uint8Array.prototype.join( [separator] )

Serializes an array by joining all array elements as a string.

var arr = new Uint8Array( [ 1, 2, 3 ] );

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

By default, the method delineates array elements using a comma ,. To specify a custom separator, provide a separator string.

var arr = new Uint8Array( [ 1, 2, 3 ] );

var str = arr.join( '|' );
// returns '1|2|3'

Uint8Array.prototype.keys()

Returns an iterator for iterating over array keys.

var arr = new Uint8Array( [ 1, 2 ] );

// Create an iterator:
var it = arr.keys();

// Iterate over keys...
var v = it.next().value;
// returns 0

v = it.next().value;
// returns 1

var bool = it.next().done;
// returns true

Uint8Array.prototype.lastIndexOf( searchElement[, fromIndex] )

Returns the index of the last array element strictly equal to a search element, iterating from right to left.

var arr = new Uint8Array( [ 1, 0, 2, 0, 1 ] );

var idx = arr.lastIndexOf( 0 );
// returns 3

idx = arr.lastIndexOf( 3 );
// returns -1

By default, the method searches the entire array (fromIndex = -1). To begin searching from a specific array index, provide a fromIndex.

var arr = new Uint8Array( [ 1, 0, 2, 0, 1 ] );

var idx = arr.lastIndexOf( 0, 2 );
// returns 1

When a fromIndex is negative, the starting index is resolved relative to the last array element.

var arr = new Uint8Array( [ 1, 0, 2, 0, 1 ] );

var idx = arr.lastIndexOf( 0, -3 );
// returns 1

Uint8Array.prototype.map( fcn[, thisArg] )

Maps each array element to an element in a new array having the same data type as the host array.

function fcn( v ) {
    return v * 2;
}

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.map( fcn );
// returns <Uint8Array>[ 2, 4, 6 ]

A callback is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function fcn( v ) {
    this.count += 1;
    return v * 2;
}

var ctx = {
    'count': 0
};

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.map( fcn, ctx );

var n = ctx.count;
// returns 3

Uint8Array.prototype.reduce( fcn[, initialValue] )

Applies a function against an accumulator and each element in an array and returns the accumulated result.

function fcn( acc, v ) {
    return acc + ( v*v );
}

var arr = new Uint8Array( [ 2, 1, 3 ] );

var v = arr.reduce( fcn );
// returns 12

If not provided an initial value, the method invokes a provided function with the first array element as the first argument and the second array element as the second argument.

If provided an initial value, the method invokes a provided function with the initial value as the first argument and the first array element as the second argument.

function fcn( acc, v ) {
    return acc + ( v*v );
}

var arr = new Uint8Array( [ 2, 1, 3 ] );

var v = arr.reduce( fcn, 0 );
// returns 14

A callback is provided four arguments:

acc: accumulated result
value: array element
index: array index
arr: array on which the method is invoked

Uint8Array.prototype.reduceRight( fcn[, initialValue] )

Applies a function against an accumulator and each element in an array and returns the accumulated result, iterating from right to left.

function fcn( acc, v ) {
    return acc + ( v*v );
}

var arr = new Uint8Array( [ 2, 1, 3 ] );

var v = arr.reduceRight( fcn );
// returns 8

If not provided an initial value, the method invokes a provided function with the last array element as the first argument and the second-to-last array element as the second argument.

If provided an initial value, the method invokes a provided function with the initial value as the first argument and the last array element as the second argument.

function fcn( acc, v ) {
    return acc + ( v*v );
}

var arr = new Uint8Array( [ 2, 1, 3 ] );

var v = arr.reduce( fcn, 0 );
// returns 14

A callback is provided four arguments:

acc: accumulated result
value: array element
index: array index
arr: array on which the method is invoked

Uint8Array.prototype.reverse()

Reverses an array in-place (thus mutating the array on which the method is invoked).

var arr = new Uint8Array( [ 2, 0, 3 ] );

// Reverse the array:
arr.reverse();

var v = arr[ 0 ];
// returns 3

v = arr[ 1 ];
// returns 0

v = arr[ 2 ];
// returns 2

Uint8Array.prototype.set( arr[, offset] )

Sets array elements.

var arr = new Uint8Array( [ 1, 2, 3 ] );
// returns <Uint8Array>[ 1, 2, 3 ]

// Set the first two array elements:
arr.set( [ 4, 5 ] );

var v = arr[ 0 ];
// returns 4

v = arr[ 1 ];
// returns 5

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

var arr = new Uint8Array( [ 1, 2, 3 ] );
// returns <Uint8Array>[ 1, 2, 3 ]

// Set the last two array elements:
arr.set( [ 4, 5 ], 1 );

var v = arr[ 1 ];
// returns 4

v = arr[ 2 ];
// returns 5

Uint8Array.prototype.slice( [begin[, end]] )

Copies array elements to a new array with the same underlying data type as the host array.

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.slice();

var bool = ( arr1 === arr2 );
// returns false

bool = ( arr1.buffer === arr2.buffer );
// returns false

var v = arr2[ 0 ];
// returns 1

v = arr2[ 1 ];
// returns 2

v = arr2[ 2 ];
// returns 3

By default, the method copies elements beginning with the first array element. To specify an alternative array index at which to begin copying, provide a begin index (inclusive).

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.slice( 1 );

var len = arr2.length;
// returns 2

var v = arr2[ 0 ];
// returns 2

v = arr2[ 1 ];
// returns 3

By default, the method copies all array elements after begin. To specify an alternative array index at which to end copying, provide an end index (exclusive).

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.slice( 0, 2 );

var len = arr2.length;
// returns 2

var v = arr2[ 0 ];
// returns 1

v = arr2[ 1 ];
// returns 2

When a begin and/or end index is negative, the respective index is determined relative to the last array element.

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.slice( -arr1.length, -1 );

var len = arr2.length;
// returns 2

var v = arr2[ 0 ];
// returns 1

v = arr2[ 1 ];
// returns 2

Uint8Array.prototype.some( predicate[, thisArg] )

Tests whether at least one array element passes a test implemented by a predicate function.

function predicate( v ) {
    return ( v >= 2 );
}

var arr = new Uint8Array( [ 1, 2 ] );

var bool = arr.some( predicate );
// returns true

A predicate function is provided three arguments:

value: array element
index: array index
arr: array on which the method is invoked

To set the callback execution context, provide a thisArg.

function predicate( v ) {
    this.count += 1;
    return ( v >= 2 );
}

var ctx = {
    'count': 0
};

var arr = new Uint8Array( [ 1, 1 ] );

var bool = arr.some( predicate, ctx );
// returns false

var n = ctx.count;
// returns 2

Uint8Array.prototype.sort( [compareFunction] )

Sorts an array in-place (thus mutating the array on which the method is invoked).

var arr = new Uint8Array( [ 2, 3, 0 ] );

// Sort the array (in ascending order):
arr.sort();

var v = arr[ 0 ];
// returns 0

v = arr[ 1 ];
// returns 2

v = arr[ 2 ];
// returns 3

By default, the method sorts array elements in ascending order. To impose a custom order, provide a compareFunction.

function descending( a, b ) {
    return b - a;
}

var arr = new Uint8Array( [ 2, 3, 0 ] );

// Sort the array (in descending order):
arr.sort( descending );

var v = arr[ 0 ];
// returns 3

v = arr[ 1 ];
// returns 2

v = arr[ 2 ];
// returns 0

The comparison function is provided two array elements, a and b, per invocation, and its return value determines the sort order as follows:

If the comparison function returns a value less than zero, then the method sorts a to an index lower than b (i.e., a should come before b).
If the comparison function returns a value greater than zero, then the method sorts a to an index higher than b (i.e., b should come before a).
If the comparison function returns zero, then the relative order of a and b should remain unchanged.

Uint8Array.prototype.subarray( [begin[, end]] )

Creates a new typed array view over the same underlying ArrayBuffer and with the same underlying data type as the host array.

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.subarray();
// returns <Uint8Array>[ 1, 2, 3 ]

var bool = ( arr1.buffer === arr2.buffer );
// returns true

By default, the method creates a typed array view beginning with the first array element. To specify an alternative array index at which to begin, provide a begin index (inclusive).

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.subarray( 1 );
// returns <Uint8Array>[ 2, 3 ]

var bool = ( arr1.buffer === arr2.buffer );
// returns true

By default, the method creates a typed array view which includes all array elements after begin. To limit the number of array elements after begin, provide an end index (exclusive).

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.subarray( 0, 2 );
// returns <Uint8Array>[ 1, 2 ]

var bool = ( arr1.buffer === arr2.buffer );
// returns true

When a begin and/or end index is negative, the respective index is determined relative to the last array element.

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.subarray( -arr1.length, -1 );
// returns <Uint8Array>[ 1, 2 ]

var bool = ( arr1.buffer === arr2.buffer );
// returns true

If the method is unable to resolve indices to a non-empty array subsequence, the method returns an empty typed array.

var arr1 = new Uint8Array( [ 1, 2, 3 ] );

var arr2 = arr1.subarray( 10, -1 );
// returns <Uint8Array>[]

Uint8Array.prototype.toLocaleString( [locales[, options]] )

Serializes an array as a locale-specific string.

var arr = new Uint8Array( [ 1, 2, 3 ] );

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

Uint8Array.prototype.toString()

Serializes an array as a string.

var arr = new Uint8Array( [ 1, 2, 3 ] );

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

Uint8Array.prototype.values()

Returns an iterator for iterating over array elements.

var arr = new Uint8Array( [ 1, 2 ] );

// Create an iterator:
var it = arr.values();

// Iterate over array elements...
var v = it.next().value;
// returns 1

v = it.next().value;
// returns 2

var bool = it.next().done;
// returns true

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var ctor = require( '@stdlib/array-uint8' );

var arr;
var i;

arr = new ctor( 10 );
for ( i = 0; i < arr.length; i++ ) {
    arr[ i ] = round( randu()*100.0 );
}
console.log( arr );

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.