contains

Test if an array-like value contains a search value.

Installation

npm install @stdlib/assert-contains

Usage

var contains = require( '@stdlib/assert-contains' );

contains( value, searchValue[, position] )

Tests if value contains a search value.

var v = contains( [ 1, 2, 3 ], 2 );
// returns true

When value is a string, the function checks whether the characters of a search string are found in the input string.

var v = contains( 'Hello World', 'World' );
// returns true

When value is an array-like object, but not a string, the function checks whether the input value contains an element which is the same value as the specified search value.

var arr = [ null, NaN, 2, 'abc', {} ];

var v = contains( arr, NaN ); // NaNs are considered equal
// returns true

v = contains( arr, {} );
// returns false

v = contains( arr, 'ab' );
// returns false

Search is case-sensitive.

var v = contains( 'Hello World', 'world' );
// returns false

To start searching at a specified index, provide a position argument.

var v = contains( 'Hello World', 'Hello', 6 );
// returns false

v = contains( [ true, NaN, false ], true, 1 );
// returns false

If not provided an array-like object, the function throws an error.

var v = contains( false, 'abc' );
// throws <TypeError>

If not provided an integer-valued position argument, the function throws an error.

var v = contains( 'hello', 'e', 2.5 );
// throws <TypeError>

Notes

• For strings, the function is modeled after String.prototype.includes, part of the ECMAScript 6 specification. This function is different from a call to String.prototype.includes.call insofar as type-checking is performed for all arguments.
• The function does distinguish between positive and negative zero (see @stdlib/assert-is-same-value).
• If position < 0, the search is performed for the entire input array or string.

Examples

var contains = require( '@stdlib/assert-contains' );

var bool = contains( 'last man standing', 'stand' );
// returns true

bool = contains( [ 1, 2, 3, 4 ], 2 );
// returns true

bool = contains( 'presidential election', 'president' );
// returns true

bool = contains( [ NaN, 2, 3, 4 ], NaN );
// returns true

bool = contains( 'javaScript', 'js' );
// returns false

bool = contains( 'Hidden Treasures', '' );
// returns true

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

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.