117 lines
4.5 KiB
Markdown
117 lines
4.5 KiB
Markdown
<h1 align=center>
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<a href="http://chaijs.com" title="Chai Documentation">
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<img alt="ChaiJS" src="http://chaijs.com/img/chai-logo.png"/> deep-eql
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</a>
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</h1>
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<p align=center>
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Improved deep equality testing for [node](http://nodejs.org) and the browser.
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</p>
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<p align=center>
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<a href="./LICENSE">
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<img
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alt="license:mit"
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src="https://img.shields.io/badge/license-mit-green.svg?style=flat-square"
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/>
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</a><a href="https://github.com/chaijs/deep-eql/releases">
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<img
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alt="tag:?"
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src="https://img.shields.io/github/tag/chaijs/deep-eql.svg?style=flat-square"
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/>
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</a><a href="https://travis-ci.org/chaijs/deep-eql">
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<img
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alt="build:?"
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src="https://img.shields.io/travis/chaijs/deep-eql/master.svg?style=flat-square"
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/>
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</a><a href="https://coveralls.io/r/chaijs/deep-eql">
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<img
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alt="coverage:?"
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src="https://img.shields.io/coveralls/chaijs/deep-eql/master.svg?style=flat-square"
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/>
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</a><a href="https://www.npmjs.com/packages/deep-eql">
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<img
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alt="code quality:?"
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src="https://img.shields.io/codacy/6de187aa62274dbea6e69a3c27e798da.svg?style=flat-square"
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/>
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</a><a href="https://www.npmjs.com/packages/deep-eql">
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<img
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alt="dependencies:?"
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src="https://img.shields.io/npm/dm/deep-eql.svg?style=flat-square"
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/>
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</a><a href="">
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<img
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alt="devDependencies:?"
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src="https://img.shields.io/david/chaijs/deep-eql.svg?style=flat-square"
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/>
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</a><a href="https://github.com/nodejs/LTS#lts-schedule1">
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<img
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alt="Supported Node Version: 4+"
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src="https://img.shields.io/badge/node-4+-43853d.svg?style=flat-square"
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/>
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</a>
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<br/>
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<a href="https://saucelabs.com/u/chaijs-deep-eql">
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<img
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alt="Selenium Test Status"
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src="https://saucelabs.com/browser-matrix/chaijs-deep-eql.svg"
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/>
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</a>
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<br>
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<a href="https://chai-slack.herokuapp.com/">
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<img
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alt="Join the Slack chat"
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src="https://img.shields.io/badge/slack-join%20chat-E2206F.svg?style=flat-square"
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/>
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</a>
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<a href="https://gitter.im/chaijs/deep-eql">
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<img
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alt="Join the Gitter chat"
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src="https://img.shields.io/badge/gitter-join%20chat-D0104D.svg?style=flat-square"
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/>
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</a>
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</p>
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## What is Deep-Eql?
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Deep Eql is a module which you can use to determine if two objects are "deeply" equal - that is, rather than having referential equality (`a === b`), this module checks an object's keys recursively, until it finds primitives to check for referential equality. For more on equality in JavaScript, read [the comparison operators article on mdn](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators).
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As an example, take the following:
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```js
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1 === 1 // These are primitives, they hold the same reference - they are strictly equal
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1 == '1' // These are two different primitives, through type coercion they hold the same value - they are loosely equal
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{ a: 1 } !== { a: 1 } // These are two different objects, they hold different references and so are not strictly equal - even though they hold the same values inside
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{ a: 1 } != { a: 1 } // They have the same type, meaning loose equality performs the same check as strict equality - they are still not equal.
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var deepEql = require("deep-eql");
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deepEql({ a: 1 }, { a: 1 }) === true // deepEql can determine that they share the same keys and those keys share the same values, therefore they are deeply equal!
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```
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## Installation
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### Node.js
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`deep-eql` is available on [npm](http://npmjs.org).
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$ npm install deep-eql
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## Usage
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The primary export of `deep-eql` is function that can be given two objects to compare. It will always return a boolean which can be used to determine if two objects are deeply equal.
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### Rules
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- Strict equality for non-traversable nodes according to [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is):
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- `eql(NaN, NaN).should.be.true;`
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- `eql(-0, +0).should.be.false;`
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- All own and inherited enumerable properties are considered:
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- `eql(Object.create({ foo: { a: 1 } }), Object.create({ foo: { a: 1 } })).should.be.true;`
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- `eql(Object.create({ foo: { a: 1 } }), Object.create({ foo: { a: 2 } })).should.be.false;`
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- Arguments are not Arrays:
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- `eql([], arguments).should.be.false;`
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- `eql([], Array.prototype.slice.call(arguments)).should.be.true;`
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- Error objects are compared by reference (see https://github.com/chaijs/chai/issues/608):
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- `eql(new Error('msg'), new Error('msg')).should.be.false;`
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- `var err = new Error('msg'); eql(err, err).should.be.true;`
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