npm package: @stdlib/assert-is-json
Description: Test if a value is a parseable JSON string.
Author: The Stdlib Authors
Latest version: 0.2.3

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# isJSON

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Test if a value is a parseable JSON string.

<section class="installation">

## Installation

```bash
npm install @stdlib/assert-is-json
```

</section>

<section class="usage">

## Usage

```javascript
var isJSON = require( '@stdlib/assert-is-json' );
```

#### isJSON( value )

Tests if a `value` is a parseable JSON `string`.

```javascript
var value = '{"a":5}';

var bool = isJSON( value );
// returns true
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The implementation validates that the input `value` is a `string` literal. For all other inputs, the method returns `false`.

-   The implementation validates that a `string` begins with either `[` or `{` and ends with a corresponding `]` or `}`, respectively. Hence, the method will return `false` for the following `strings`, despite `JSON.parse` accepting their input:

    -   `'<number>'` (e.g., `'5'`)
    -   `'<boolean>'` (e.g., `'true'`)
    -   `'null'`

-   The implementation wraps `JSON.parse` inside a `try/catch`. Hence, this function cannot be optimized by the compiler during runtime. Nevertheless, using this function is better than embedding a `try/catch` within a larger `function` which could be optimized in the absence of a `try/catch`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var isJSON = require( '@stdlib/assert-is-json' );

var bool = isJSON( '{"a":5}' );
// returns true

bool = isJSON( '{a":5}' );
// returns false
```

</section>

<!-- /.examples -->

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<section class="related">

</section>

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<section class="main-repo" >

* * *

## Notice

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].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[npm-image]: http://img.shields.io/npm/v/@stdlib/assert-is-json.svg
[npm-url]: https://npmjs.org/package/@stdlib/assert-is-json

[test-image]: https://github.com/stdlib-js/assert-is-json/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/assert-is-json/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/assert-is-json/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/assert-is-json?branch=main

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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-is-json/tree/deno
[deno-readme]: https://github.com/stdlib-js/assert-is-json/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/assert-is-json/tree/umd
[umd-readme]: https://github.com/stdlib-js/assert-is-json/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/assert-is-json/tree/esm
[esm-readme]: https://github.com/stdlib-js/assert-is-json/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/assert-is-json/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/assert-is-json/main/LICENSE

</section>

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