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

!example image

Inspired by the 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 and updated the dependencies so they work with modern stacks.

Install

``bash
yarn add react-diff-viewer-continued

or

npm i react-diff-viewer-continued

or

pnpm add react-diff-viewer-continued
`

Usage

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

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 \| Object | '' | Old value as string (or Object if using diffJson). |
| newValue | string \| Object | '' | New value as string (or Object if using diffJson). |
| splitView | boolean | true | Switch between unified and split view. |
| disableWordDiff | boolean | false | Show and hide word diff in a diff line. |
| compareMethod | DiffMethod \| (string, string) => diff.Change[] | DiffMethod.CHARS | Uses an existing diff method when a DiffMethod enum is passed. If a function is passed, that function is used as the diff method.

JsDiff text diff method used for diffing strings. Check out the guide to use different methods. |
| renderGutter | (diffData) => ReactNode | undefined | Function that can be used to render an extra gutter with various information next to the line number. |
| hideLineNumbers | boolean | false | Show and hide line numbers. |
| alwaysShowLines | string[] | [] | List of lines to always be shown, regardless of diff status. 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. extraLinesSurroundingDiff applies to these lines as well. |
| 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) => void |
| highlightLines | 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
pnpm install
pnpm build # or use yarn build:watch
pnpm start:examples
``

Check package.json for more build scripts.

Contributors

Eric M. 💻

Andrei Kovalevsky 💻

Chang Hyun Kim 💻

License

MIT