shift

Remove and return the first element of a collection.

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 );