Test if an array-like value contains a search value.
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> Test if an array-like value contains a search value.
``bash`
npm install @stdlib/assert-contains
`javascript`
var contains = require( '@stdlib/assert-contains' );
#### contains( value, searchValue\[, position] )
Tests if value contains a search value.
`javascript`
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.
`javascript`
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][@stdlib/assert/is-same-value] as the specified search value.
`javascript
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.
`javascript`
var v = contains( 'Hello World', 'world' );
// returns false
To start searching at a specified index, provide a position argument.
`javascript
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.
`javascript`
var v = contains( false, 'abc' );
// throws
If not provided an integer-valued position argument, the function throws an error.
`javascript`
var v = contains( 'hello', 'e', 2.5 );
// throws
*
- For strings, the function is modeled after [String.prototype.includes][mdn-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.@stdlib/assert-is-same-value
- The function does distinguish between positive and negative zero (see [][@stdlib/assert/is-same-value]).position < 0
- If , the search is performed for the entire input array or string.
`javascript
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
`
*
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
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---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[stdlib]: https://github.com/stdlib-js/stdlib
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/assert-contains/tree/deno
[deno-readme]: https://github.com/stdlib-js/assert-contains/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/assert-contains/tree/umd
[umd-readme]: https://github.com/stdlib-js/assert-contains/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/assert-contains/tree/esm
[esm-readme]: https://github.com/stdlib-js/assert-contains/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/assert-contains/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/assert-contains/main/LICENSE
[mdn-includes]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes
[@stdlib/assert/is-same-value]: https://www.npmjs.com/package/@stdlib/assert-is-same-value