npm package: @stdlib/proxy-ctor
Description: Proxy object.
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>
  <p>The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.</p>
  <p>When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.</p>
  <p>To join us in bringing numerical computing to the web, get started by checking us out on <a href="https://github.com/stdlib-js/stdlib">GitHub</a>, and please consider <a href="https://opencollective.com/stdlib">financially supporting stdlib</a>. We greatly appreciate your continued support!</p>
</details>

# Proxy

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

> [Proxy][mdn-proxy] object.

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<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/proxy-ctor
```

</section>

<section class="usage">

## Usage

```javascript
var Proxy = require( '@stdlib/proxy-ctor' );
```

#### Proxy( target, handlers )

Returns a [proxy][mdn-proxy] object implementing custom behavior for specified object operations.

```javascript
function get( target, property ) {
    return target[ property ] * 2.0;
}

var handlers = {
    'get': get
};

var p = new Proxy( {}, handlers );

p.a = 3.14;

var v = p.a;
// returns 6.28
```

A `handlers` argument should be an `object` whose properties are functions (called "**traps**") which define the behavior of the proxy when performing operations. The following traps are supported:

-   `getPrototypeOf( target )`

    -   Trap for `Object.getPrototypeOf()`. Can be used to intercept the `instanceof` operator. The method must return an `object` or `null`.

-   `setPrototypeOf( target, prototype )`

    -   Trap for `Object.setPrototypeOf()`. The method must return a `boolean` indicating if the prototype was successfully set.

-   `isExtensible( target )`

    -   Trap for `Object.isExtensible()`. The method must return a `boolean`.

-   `preventExtensions( target )`

    -   Trap for `Object.preventExtensions()`. The method must return a `boolean`.

-   `getOwnPropertyDescriptor( target, property )`

    -   Trap for `Object.getOwnPropertyDescriptor()`. The method must return an `object` or `undefined`.

-   `defineProperty( target, property, descriptor )`

    -   Trap for `Object.defineProperty()`. The method must return a `boolean` indicating whether the operation succeeded.

-   `has( target, property )`

    -   Trap for the `in` operator. The method must return a `boolean`.

-   `get( target, property, receiver )`

    -   Trap for retrieving property values. The method can return any value.

-   `set( target, property, value, receiver )`

    -   Trap for setting property values. The method should return a `boolean` indicating whether assignment succeeded.

-   `deleteProperty( target, property )`

    -   Trap for the `delete` operator. The method must return a `boolean` indicating whether operation succeeded.

-   `ownKeys( target )`

    -   Trap for `Object.keys`, `Object.getOwnPropertyNames()`, and `Object.getOwnPropertySymbols()`. The method must return an enumerable `object`.

-   `apply( target, thisArg, argumentsList )`

    -   Trap for a function call. The method can return any value.

-   `construct( target, argumentsList, newTarget )`

    -   Trap for the `new` operator. The method must return an `object`.

All traps are **optional**. If a trap is not defined, the default behavior is to forward the operation to the target.

</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 Float64Array = require( '@stdlib/array-float64' );
var Proxy = require( '@stdlib/proxy-ctor' );

var handlers;
var arr;
var p;
var i;

// Create a new typed array:
arr = new Float64Array( 10 );
for ( i = 0; i < arr.length; i++ ) {
    arr[ i ] = i;
}

// Define a "trap" when retrieving property values:
function get( obj, prop ) {
    if ( prop === 'length' ) {
        return obj.length;
    }
    return obj[ prop ] * 2.0;
}

// Define the proxy handlers:
handlers = {
    'get': get
};

// Create a proxy:
p = new Proxy( arr, handlers );

// Access array values...
for ( i = 0; i < p.length; i++ ) {
    console.log( 'arr[%d] = %d', i, p[ i ] );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

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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>

<!-- /.stdlib -->

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<section class="links">

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

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

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

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[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

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

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/proxy-ctor/main/LICENSE

[mdn-proxy]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy

</section>

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