npm package: @stdlib/utils-try-then
Description: If a function does not throw, return the function return value; otherwise, return the return value of a second function.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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# trythen

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

> If a function does not throw, return the function return value; otherwise, return the return value of a second function.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/utils-try-then
```

</section>

<section class="usage">

## Usage

```javascript
var trythen = require( '@stdlib/utils-try-then' );
```

#### trythen( x, y )

If a function `x` does not throw, returns the return value of `x`; otherwise, returns the return value of a second function `y`.

```javascript
function x1() {
    return 1.0;
}

function x2() {
    throw new Error( 'beep' );
}

function y() {
    return -1.0;
}

var z = trythen( x1, y );
// returns 1.0

z = trythen( x2, y );
// returns -1.0
```

The function `y` is provided a single argument:

-   **error**: the error thrown by `x`.

```javascript
var randu = require( '@stdlib/random-base-randu' );

function x() {
    if ( randu() < 0.5 ) {
        throw new Error( 'beep' );
    }
    throw new TypeError( 'boop' );
}

function y( err ) {
    if ( err instanceof TypeError ) {
        return 'boops';
    }
    return 'beeps';
}

var z = trythen( x, y );
// returns <string>
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var randu = require( '@stdlib/random-base-randu' );
var ceil = require( '@stdlib/math-base-special-ceil' );
var repeatString = require( '@stdlib/string-repeat' );
var trythen = require( '@stdlib/utils-try-then' );

var z;
var i;

function x() {
    if ( randu() < 0.9 ) {
        throw new Error( 'BOOP' );
    }
    return repeatString( 'BOOP', ceil( randu()*3.0 ) );
}

function y() {
    return repeatString( 'beep', ceil( randu()*5.0 ) );
}

for ( i = 0; i < 100; i++ ) {
    z = trythen( x, y );
    console.log( z );
}
```

</section>

<!-- /.examples -->

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</section>

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/utils-try-catch`][@stdlib/utils/try-catch]</span><span class="delimiter">: </span><span class="description">if a function does not throw, return the function return value; otherwise, return `y`.</span>
-   <span class="package-name">[`@stdlib/utils-async/try-then`][@stdlib/utils/async/try-then]</span><span class="delimiter">: </span><span class="description">if a function does not return an error, invoke a callback with the function result; otherwise, invoke a second function.</span>

</section>

<!-- /.related -->

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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-url]: https://npmjs.org/package/@stdlib/utils-try-then

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[umd]: https://github.com/umdjs/umd
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[umd-url]: https://github.com/stdlib-js/utils-try-then/tree/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-try-then/main/LICENSE

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[@stdlib/utils/try-catch]: https://www.npmjs.com/package/@stdlib/utils-try-catch

[@stdlib/utils/async/try-then]: https://www.npmjs.com/package/@stdlib/utils-async-try-then

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</section>

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