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shift

Remove and return the first element of a collection.

Installation

npm install @stdlib/utils-shift

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var shift = require( '@stdlib/utils-shift' );

shift( collection )

Removes and returns the first element of a collection. A collection may be either an Array, Typed Array, or an array-like Object (i.e., an Object having a valid writable length property).

var arr = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];

var out = shift( arr );
// returns [ [ 2.0, 3.0, 4.0, 5.0 ], 1.0 ]

var bool = ( out[ 0 ] === arr );
// returns true

var lastValue = out[ 1 ];
// returns 1.0

In contrast to Array.prototype.shift which returns only the removed element, the function also returns the shortened collection. For typed arrays having a length greater than 0, the returned collection is a new typed array view.

var Float64Array = require( '@stdlib/array-float64' );

var arr = new Float64Array( 2 );
arr[ 0 ] = 1.0;
arr[ 1 ] = 2.0;

var out = shift( arr );
// returns [ <Float64Array>[ 2.0 ], 1.0 ]

var bool = ( out[ 0 ] === arr );
// returns false

bool = ( out[ 0 ].buffer === arr.buffer );
// returns true

var lastValue = out[ 1 ];
// returns 1.0

Notes

• When provided a typed array, the function does not change the underlying ArrayBuffer. The function returns a new typed array view whose length is one less than the input typed array length. Accordingly, the function does not reduce the memory footprint of an input typed array.

Examples

var Float64Array = require( '@stdlib/array-float64' );
var shift = require( '@stdlib/utils-shift' );

var arr;
var out;
var i;

arr = new Float64Array( 100 );
for ( i = 0; i < 100; i++ ) {
    out = shift( arr );
    arr = out[ 0 ];
    console.log( 'Length: %d', arr.length );
}
console.log( arr );

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See Also

• @stdlib/utils-pop: remove and return the last element of a collection.
• @stdlib/utils-push: add one or more elements to the end of a collection.
• @stdlib/utils-unshift: add one or more elements to the beginning of a collection.

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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.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.