react-fast-compare

What is react-fast-compare?

The react-fast-compare package is a fast deep equal comparison for React. It is optimized for comparing the props or state of React components, although it can be used to compare any data structures. It is particularly useful in shouldComponentUpdate methods to determine if re-rendering is necessary.

What are react-fast-compare's main functionalities?

Deep comparison of objects and arrays

This feature allows for deep comparison of objects and arrays to determine if they are structurally identical.

import isEqual from 'react-fast-compare';

const obj1 = { a: 1, b: { c: 2 } };
const obj2 = { a: 1, b: { c: 2 } };

const areEqual = isEqual(obj1, obj2); // true

Comparison within React lifecycle methods

This code sample demonstrates how react-fast-compare can be used within a React component's shouldComponentUpdate lifecycle method to prevent unnecessary re-renders.

import React from 'react';
import isEqual from 'react-fast-compare';

class MyComponent extends React.Component {
  shouldComponentUpdate(nextProps) {
    return !isEqual(this.props, nextProps);
  }

  render() {
    // Component rendering logic
  }
}

Other packages similar to react-fast-compare

lodash.isequal

Lodash's isEqual method provides deep comparison of objects and arrays, similar to react-fast-compare. However, lodash is a general utility library that includes a wide range of functions, which may result in a larger bundle size if only isEqual is needed.

deep-equal

The deep-equal package is another library that can perform deep equality checks. It is not specifically optimized for React and may not be as performant as react-fast-compare in the context of comparing React props and state.

fast-deep-equal

fast-deep-equal is a package that offers a fast deep equality comparison. It is similar to react-fast-compare but is not specifically tailored for React, although it can be used in any JavaScript environment.

README

react-fast-compare

The fastest deep equal comparison for React. Really fast general-purpose deep comparison. Great forshouldComponentUpdate. This is a fork of the brilliant fast-deep-equal with some extra handling for React.

(Check out the benchmarking details.)

Install

$ yarn add react-fast-compare
# or
$ npm install react-fast-compare

Highlights

• ES5 compatible; works in node.js (0.10+) and browsers (IE9+)
• deeply compares any value (besides objects with circular references)
• handles React-specific circular references, like elements
• checks equality Date and RegExp objects
• should be just as fast as fast-deep-equal for general use, and faster for React use
• small: under 600 bytes minified+gzipped

Usage

const isEqual = require("react-fast-compare");

// general usage
console.log(isEqual({ foo: "bar" }, { foo: "bar" })); // true

// react usage
class ExpensiveRenderer extends React.Component {
  shouldComponentUpdate(nextProps) {
    return !isEqual(this.props, nextProps);
  }
  render() {
    // ...
  }
}

Do I Need shouldComponentUpdate?

What's faster than a really fast deep comparison? No deep comparison at all.

—This Readme

Deep checks in React's shouldComponentUpdate should not be used blindly. First, see if a PureComponent would work for you. If it won't (if you need deep checks), it's wise to make sure you've correctly indentified the bottleneck in your application by profiling the performance. After you've determined that you do need deep equality checks and you've identified the minimum number of places to apply them, then this library may be for you! For more information about making your app faster, check out the Optimizing Performance section of the React docs.

Benchmarking this Library

All tests carried out locally on a MacBook. The absolute values are much less important than the relative differences between packages.

Benchmarking source can be found here. Each "operation" consists of running all relevant tests. The React benchmark uses both the generic tests and the react tests; these runs will be slower simply because there are more tests in each operation.

Generic Data

react-fast-compare x 207,503 ops/sec ±0.54% (92 runs sampled)
fast-deep-equal x 195,006 ops/sec ±0.70% (91 runs sampled)
lodash.isEqual x 43,778 ops/sec ±0.55% (91 runs sampled)
nano-equal x 198,036 ops/sec ±0.37% (95 runs sampled)
shallow-equal-fuzzy x 173,023 ops/sec ±0.59% (95 runs sampled)
  fastest: react-fast-compare

react-fast-compare and fast-deep-equal should be the same speed for these tests; any difference is just noise. react-fast-compare won't be faster than fast-deep-equal, because it's based on it.

React and Generic Data

react-fast-compare x 187,628 ops/sec ±0.58% (93 runs sampled)
fast-deep-equal x 477 ops/sec ±0.55% (91 runs sampled)
lodash.isEqual x 35,100 ops/sec ±0.16% (95 runs sampled)
nano-equal x 468 ops/sec ±0.53% (94 runs sampled)
shallow-equal-fuzzy x 684 ops/sec ±0.43% (92 runs sampled)
  fastest: react-fast-compare

Three of these packages cannot handle comparing React elements (which are circular): fast-deep-equal, nano-equal, and shallow-equal-fuzzy.

Running Benchmarks

$ yarn install
$ yarn run benchmark

fast-deep-equal Versioning

react-fast-compare@2.0.0 tracks fast-deep-equal@2.0.1

License

MIT

Contributing

Please see our contributions guide.

Changelog

2.0.4 (2018-11-09)

• #39. Fix react-native bug introduced by DOM element checking.