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Remove and return the first element of a collection.
import shift from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-shift@esm/index.mjs';
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.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
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
- 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.
<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
import shift from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-shift@esm/index.mjs';
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 );
</script>
</body>
</html>
@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.
This package is part of stdlib, a standard library 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.
See LICENSE.
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