A simple and beautiful text diff viewer component made with Diff and React.

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.

Most credit goes to Pranesh Ravi who created the original diff viewer. I've just made a few modifications.

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 (

);
};
}
`

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 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 |
| onLineNumberClick | function | undefined | Event handler for line number click. (lineId: string, type: number) => 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 |
| 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

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

// Load Prism JS

`

`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 => (


      style={{ display: 'inline' }}

      dangerouslySetInnerHTML={{

        __html: Prism.highlight(str, Prism.languages.javascript),

      }}

    />

  );



  render = () => {

    return (

              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). 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 (

              oldValue={oldCode}

        newValue={newCode}

        compareMethod={DiffMethod.WORDS}

        splitView={true}

      />

    );

  };

}

`



Overriding Styles



React Diff Viewer uses emotion 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 => (

          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 (

              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