npm package: @john.herr/react-diff-viewer
Description: A simple and beautiful text diff viewer component made with diff and React
Author: Pranesh Ravi
Latest version: 3.1.2


<p align="center">
  <img src='https://i.ibb.co/DKrGhVQ/Frame-1-1.png' width="100%" alt='React Diff Viewer' />
</p>
<br/>

[![Build Status](https://travis-ci.com/praneshr/react-diff-viewer.svg?branch=master)](https://travis-ci.com/praneshr/react-diff-viewer)
[![npm version](https://badge.fury.io/js/react-diff-viewer.svg)](https://badge.fury.io/js/react-diff-viewer)
[![GitHub license](https://img.shields.io/github/license/praneshr/react-diff-viewer.svg)](https://github.com/praneshr/react-diff-viewer/blob/master/LICENSE)

A simple and beautiful text diff viewer component made with [Diff](https://github.com/kpdecker/jsdiff) and [React](https://reactjs.org).

Inspired from Github diff viewer, it includes features like split view, inline view, word diff, line highlight and more. It is highly customizable and it supports almost all languages.

Check [here](https://github.com/praneshr/react-diff-viewer/tree/v2.0) for v2.0

## Install

```bash
yarn add react-diff-viewer

# or

npm i react-diff-viewer
```

## Usage

```javascript
import React, { PureComponent } from 'react';
import ReactDiffViewer from 'react-diff-viewer';

const oldCode = `
const a = 10
const b = 10
const c = () => console.log('foo')

if(a > 10) {
  console.log('bar')
}

console.log('done')
`;
const newCode = `
const a = 10
const boo = 10

if(a === 10) {
  console.log('bar')
}
`;

class Diff extends PureComponent {
  render = () => {
    return (
      <ReactDiffViewer oldValue={oldCode} newValue={newCode} splitView={true} />
    );
  };
}
```

## Props

| Prop                      | Type            | Default                        | Description                                                                                                                                                                                                                                                                                                                                                                                                      |
| ------------------------- | --------------- | ------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| oldValue                  | `string`        | `''`                           | Old value as string.                                                                                                                                                                                                                                                                                                                                                                                             |
| newValue                  | `string`        | `''`                           | New value as string.                                                                                                                                                                                                                                                                                                                                                                                             |
| splitView                 | `boolean`       | `true`                         | Switch between `unified` and `split` view.                                                                                                                                                                                                                                                                                                                                                                       |
| disableWordDiff           | `boolean`       | `false`                        | Show and hide word diff in a diff line.                                                                                                                                                                                                                                                                                                                                                                          |
| compareMethod             | `DiffMethod`    | `DiffMethod.CHARS`             | JsDiff text diff method used for diffing strings. Check out the [guide](https://github.com/praneshr/react-diff-viewer/tree/v3.0.0#text-block-diff-comparison) to use different methods.                                                                                                                                                                                                                          |
| hideLineNumbers           | `boolean`       | `false`                        | Show and hide line numbers.                                                                                                                                                                                                                                                                                                                                                                                      |
| renderContent             | `function`      | `undefined`                    | Render Prop API to render code in the diff viewer. Helpful for [syntax highlighting](#syntax-highlighting)                                                                                                                                                                                                                                                                                                       |
| onLineNumberClick         | `function`      | `undefined`                    | Event handler for line number click. `(lineId: string) => void`                                                                                                                                                                                                                                                                                                                                                  |
| highlightLines            | `array[string]` | `[]`                           | List of lines to be highlighted. Works together with `onLineNumberClick`. Line number are prefixed with `L` and `R` for the left and right section of the diff viewer, respectively. For example, `L-20` means 20th line in the left pane. To highlight a range of line numbers, pass the prefixed line number as an array. For example, `[L-2, L-3, L-4, L-5]` will highlight the lines `2-5` in the left pane. |
| showDiffOnly              | `boolean`       | `true`                         | Shows only the diffed lines and folds the unchanged lines                                                                                                                                                                                                                                                                                                                                                        |
| extraLinesSurroundingDiff | `number`        | `3`                            | Number of extra unchanged lines surrounding the diff. Works along with `showDiffOnly`.                                                                                                                                                                                                                                                                                                                           |
| codeFoldMessageRenderer   | `function`      | `Expand {number} of lines ...` | Render Prop API to render code fold message.                                                                                                                                                                                                                                                                                                                                                                     |
| styles                    | `object`        | `{}`                           | To override style variables and styles. Learn more about [overriding styles](#overriding-styles)                                                                                                                                                                                                                                                                                                                 |
| useDarkTheme              | `boolean`       | `true`                         | To enable/disable dark theme.                                                                                                                                                                                                                                                                                                                                                                                    |
| leftTitle                 | `string`        | `undefined`                    | Column title for left section of the diff in split view. This will be used as the only title in inline view.                                                                                                                                                                                                                                                                                                     |
| rightTitle                | `string`        | `undefined`                    | Column title for right section of the diff in split view. This will be ignored in inline view.                                                                                                                                                                                                                                                                                                                   |
| linesOffset               | `number`        | `0`                            | Number to start count code lines from.                                                                                                                                                                                                                                                                                                                                                                           |

## Instance Methods

`resetCodeBlocks()` - Resets the expanded code blocks to it's initial state. Return `true` on successful reset and `false` during unsuccessful reset.

## Syntax Highlighting

Syntax highlighting is a bit tricky when combined with diff. Here, React Diff Viewer provides a simple render prop API to handle syntax highlighting. Use `renderContent(content: string) => JSX.Element` and your favorite syntax highlighting library to achieve this.

An example using [Prism JS](https://prismjs.com)

```html
// Load Prism CSS
<link
  href="https://cdnjs.cloudflare.com/ajax/libs/prism/1.15.0/prism.min.css"
/>

// Load Prism JS
<script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.15.0/prism.min.js"></script>
```

```javascript
import React, { PureComponent } from 'react';
import ReactDiffViewer from 'react-diff-viewer';

const oldCode = `
const a = 10
const b = 10
const c = () => console.log('foo')

if(a > 10) {
  console.log('bar')
}

console.log('done')
`;
const newCode = `
const a = 10
const boo = 10

if(a === 10) {
  console.log('bar')
}
`;

class Diff extends PureComponent {
  highlightSyntax = str => (
    <pre
      style={{ display: 'inline' }}
      dangerouslySetInnerHTML={{
        __html: Prism.highlight(str, Prism.languages.javascript),
      }}
    />
  );

  render = () => {
    return (
      <ReactDiffViewer
        oldValue={oldCode}
        newValue={newCode}
        splitView={true}
        renderContent={this.highlightSyntax}
      />
    );
  };
}
```

## Text block diff comparison

Different styles of text block diffing are possible by using the enums corresponding to variou JsDiff methods ([learn more](https://github.com/kpdecker/jsdiff/tree/v4.0.1#api)). The supported methods are as follows.

```javascript
enum DiffMethod {
  CHARS = 'diffChars',
  WORDS = 'diffWords',
  WORDS_WITH_SPACE = 'diffWordsWithSpace',
  LINES = 'diffLines',
  TRIMMED_LINES = 'diffTrimmedLines',
  SENTENCES = 'diffSentences',
  CSS = 'diffCss',
}
```

```javascript
import React, { PureComponent } from 'react';
import ReactDiffViewer, { DiffMethod } from 'react-diff-viewer';

const oldCode = `
{
  "name": "Original name",
  "description": null
}
`;
const newCode = `
{
  "name": "My updated name",
  "description": "Brand new description",
  "status": "running"
}
`;

class Diff extends PureComponent {
  render = () => {
    return (
      <ReactDiffViewer
        oldValue={oldCode}
        newValue={newCode}
        compareMethod={DiffMethod.WORDS}
        splitView={true}
      />
    );
  };
}
```

## Overriding Styles

React Diff Viewer uses [emotion](https://emotion.sh/) for styling. It also offers a simple way to override styles and style variables. You can supply different variables for both light and dark themes. Styles will be common for both themes.

Below are the default style variables and style object keys.

```javascript

// Default variables and style keys

const defaultStyles = {
  variables: {
    light: {
      diffViewerBackground: '#fff',
      diffViewerColor: '#212529',
      addedBackground: '#e6ffed',
      addedColor: '#24292e',
      removedBackground: '#ffeef0',
      removedColor: '#24292e',
      wordAddedBackground: '#acf2bd',
      wordRemovedBackground: '#fdb8c0',
      addedGutterBackground: '#cdffd8',
      removedGutterBackground: '#ffdce0',
      gutterBackground: '#f7f7f7',
      gutterBackgroundDark: '#f3f1f1',
      highlightBackground: '#fffbdd',
      highlightGutterBackground: '#fff5b1',
      codeFoldGutterBackground: '#dbedff',
      codeFoldBackground: '#f1f8ff',
      emptyLineBackground: '#fafbfc',
      gutterColor: '#212529',
      addedGutterColor: '#212529',
      removedGutterColor: '#212529',
      codeFoldContentColor: '#212529',
      diffViewerTitleBackground: '#fafbfc',
      diffViewerTitleColor: '#212529',
      diffViewerTitleBorderColor: '#eee',
    },
    dark: {
      diffViewerBackground: '#2e303c',
      diffViewerColor: '#FFF',
      addedBackground: '#044B53',
      addedColor: 'white',
      removedBackground: '#632F34',
      removedColor: 'white',
      wordAddedBackground: '#055d67',
      wordRemovedBackground: '#7d383f',
      addedGutterBackground: '#034148',
      removedGutterBackground: '#632b30',
      gutterBackground: '#2c2f3a',
      gutterBackgroundDark: '#262933',
      highlightBackground: '#2a3967',
      highlightGutterBackground: '#2d4077',
      codeFoldGutterBackground: '#21232b',
      codeFoldBackground: '#262831',
      emptyLineBackground: '#363946',
      gutterColor: '#464c67',
      addedGutterColor: '#8c8c8c',
      removedGutterColor: '#8c8c8c',
      codeFoldContentColor: '#555a7b',
      diffViewerTitleBackground: '#2f323e',
      diffViewerTitleColor: '#555a7b',
      diffViewerTitleBorderColor: '#353846',
    }
  },
  diffContainer?: {}, // style object
  diffRemoved?: {}, // style object
  diffAdded?: {}, // style object
  marker?: {}, // style object
  emptyGutter?: {}, // style object
  highlightedLine?: {}, // style object
  lineNumber?: {}, // style object
  highlightedGutter?: {}, // style object
  contentText?: {}, // style object
  gutter?: {}, // style object
  line?: {}, // style object
  wordDiff?: {}, // style object
  wordAdded?: {}, // style object
  wordRemoved?: {}, // style object
  codeFoldGutter?: {}, // style object
  codeFold?: {}, // style object
  emptyLine?: {}, // style object
  content?: {}, // style object
  titleBlock?: {}, // style object
  splitView?: {}, // style object
}
```

To override any style, just pass the new style object to the `styles` prop. New style will be computed using `Object.assign(default, override)`.

For keys other than `variables`, the value can either be an object or string interpolation.

```javascript
import React, { PureComponent } from 'react';
import ReactDiffViewer from 'react-diff-viewer';

const oldCode = `
const a = 10
const b = 10
const c = () => console.log('foo')

if(a > 10) {
  console.log('bar')
}

console.log('done')
`;
const newCode = `
const a = 10
const boo = 10

if(a === 10) {
  console.log('bar')
}
`;

class Diff extends PureComponent {
  highlightSyntax = str => (
    <span
      style={{ display: 'inline' }}
      dangerouslySetInnerHTML={{
        __html: Prism.highlight(str, Prism.languages.javascript),
      }}
    />
  );

  render = () => {
    const newStyles = {
      variables: {
        dark: {
          highlightBackground: '#fefed5',
          highlightGutterBackground: '#ffcd3c',
        },
      },
      line: {
        padding: '10px 2px',
        '&:hover': {
          background: '#a26ea1',
        },
      },
    };

    return (
      <ReactDiffViewer
        styles={newStyles}
        oldValue={oldCode}
        newValue={newCode}
        splitView={true}
        renderContent={this.highlightSyntax}
      />
    );
  };
}
```

## Local Development

```bash
yarn install
yarn build # or use yarn build:watch
yarn start:examples
```

Check package.json for more build scripts.

## License

MIT