diff2html

What is diff2html?

The diff2html npm package is a tool that allows you to convert unified diff output into HTML. It is useful for visualizing differences between files in a human-readable format, making it easier to review changes in code.

What are diff2html's main functionalities?

Generating HTML from Diff

This feature allows you to convert a unified diff string into an HTML string. The HTML output can then be embedded into a web page for visual representation of the differences.

const Diff2Html = require('diff2html');
const diffString = 'diff --git a/file1 b/file1\nindex 83db48f..f7353a0 100644\n--- a/file1\n+++ b/file1\n@@ -1 +1 @@\n-Hello World\n+Hello Diff2Html';
const outputHtml = Diff2Html.html(diffString);
console.log(outputHtml);

Generating JSON from Diff

This feature allows you to parse a unified diff string into a JSON object. The JSON output can be used for further processing or custom rendering.

const Diff2Html = require('diff2html');
const diffString = 'diff --git a/file1 b/file1\nindex 83db48f..f7353a0 100644\n--- a/file1\n+++ b/file1\n@@ -1 +1 @@\n-Hello World\n+Hello Diff2Html';
const outputJson = Diff2Html.parse(diffString);
console.log(outputJson);

Styling the Diff Output

This feature allows you to customize the HTML output with various options such as drawing a file list and matching lines. This makes the diff output more informative and easier to navigate.

const Diff2Html = require('diff2html');
const diffString = 'diff --git a/file1 b/file1\nindex 83db48f..f7353a0 100644\n--- a/file1\n+++ b/file1\n@@ -1 +1 @@\n-Hello World\n+Hello Diff2Html';
const outputHtml = Diff2Html.html(diffString, { drawFileList: true, matching: 'lines' });
console.log(outputHtml);

Other packages similar to diff2html

diff

The 'diff' package provides a set of tools to compare strings, arrays, and objects. It is more focused on providing the raw differences rather than visualizing them, making it suitable for backend processing and custom diff algorithms.

jsdiff

The 'jsdiff' package is another tool for comparing text differences. It offers a variety of diff algorithms and can output differences in several formats, including JSON. However, it does not provide built-in HTML rendering like diff2html.

git-diff

The 'git-diff' package is designed to generate diffs in the same format as the git diff command. It is useful for applications that need to integrate with git repositories but does not offer HTML rendering capabilities.

README

diff2html

diff2html generates pretty HTML diffs from git diff or unified diff output.

Table of Contents

• Features
• Online Example
• Distributions
• Usage
• Diff2HtmlUI Usage
  • Diff2HtmlUI API
  • Diff2HtmlUI Configuration
  • Diff2HtmlUI Browser
  • Diff2HtmlUI Examples
• Diff2Html Usage
  • Diff2Html API
  • Diff2Html Configuration
  • Diff2Html Browser
  • Diff2Html NPM / Node.js Library
  • Diff2Html Examples
• Troubleshooting
  • 1. Out of memory or Slow execution
• Contribute
• Contributors
• License
• Thanks

Features

• Supports git and unified diffs

• Line by line and Side by side diff

• New and old line numbers

• Inserted and removed lines

• GitHub like visual style

• Code syntax highlight

• Line similarity matching

• Easy code selection

Online Example

Go to diff2html

Distributions

• jsdelivr CDN
• WebJar
• Node Library
• NPM CLI
• Manually use from jsdelivr or build the project:
  • Browser / Bundle
    • Parser and HTML Generator
      • bundles/js/diff2html.min.js - includes the diff parser and html generator
    • Wrapper and helper adding syntax highlight, synchronized scroll, and other nice features
      • bundles/js/diff2html-ui.min.js - includes the wrapper of diff2html with highlight for all highlight.js supported languages
      • bundles/js/diff2html-ui-slim.min.js - includes the wrapper of diff2html with "the most common" highlight.js supported languages
      • bundles/js/diff2html-ui-base.min.js - includes the wrapper of diff2html without including a highlight.js implementation. You can use it without syntax highlight or by passing your own implementation with the languages you prefer
  • NPM / Node.js library
    • ES5
      • lib/diff2html.js - includes the diff parser and html generator
      • lib/ui/js/diff2html-ui.js - includes the wrapper of diff2html with highlight for all highlight.js supported languages
      • lib/ui/js/diff2html-ui-slim.js - includes the wrapper of diff2html with "the most common" highlight.js supported languages
      • lib/ui/js/diff2html-ui-base.js
    • ES6
      • lib-esm/diff2html.js - includes the diff parser and html generator
      • lib/ui/js/diff2html-ui.js - includes the wrapper of diff2html with highlight for all highlight.js supported languages
      • lib/ui/js/diff2html-ui-slim.js - includes the wrapper of diff2html with "the most common" highlight.js supported languages
      • lib/ui/js/diff2html-ui-base.js - includes the wrapper of diff2html without including a highlight.js implementation. You can use it without syntax highlight or by passing your own implementation with the languages you prefer

Usage

Diff2Html can be used in various ways as listed in the distributions section. The two main ways are:

• Diff2HtmlUI: using this wrapper makes it easy to inject the html in the DOM and adds some nice features to the diff, like syntax highlight.
• Diff2Html: using the parser and html generator directly from the library gives you complete control about what you can do with the json or html generated.

Bellow you can find more details and examples about each option.

Diff2HtmlUI Usage

Simple wrapper to ease simple tasks in the browser such as: code highlight and js effects

• Invoke Diff2html
• Inject output in DOM element
• Enable collapsible file summary list
• Enable syntax highlight of the code in the diffs

Diff2HtmlUI API

Create a Diff2HtmlUI instance

constructor(target: HTMLElement, diffInput?: string | DiffFile[]) // diff2html-ui, diff2html-ui-slim
constructor(target: HTMLElement, diffInput?: string | DiffFile[], config: Diff2HtmlUIConfig = {}, hljs?: HighlightJS) // diff2html-ui-base

Generate and inject in the document the Pretty HTML representation of the diff

draw(): void

Enable extra features

synchronisedScroll(): void
fileListToggle(startVisible: boolean): void
highlightCode(): void

Diff2HtmlUI Configuration

• synchronisedScroll: scroll both panes in side-by-side mode: true or false, default is true
• highlight: syntax highlight the code on the diff: true or false, default is true
• fileListToggle: allow the file summary list to be toggled: true or false, default is true
• fileListStartVisible: choose if the file summary list starts visible: true or false, default is false
• fileContentToggle: allow each file contents to be toggled: true or false, default is true
• All the options from Diff2Html are also valid configurations in Diff2HtmlUI

Diff2HtmlUI Browser

Mandatory HTML resource imports

<!-- CSS -->
<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/diff2html/bundles/css/diff2html.min.css" />

<!-- Javascripts -->
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/diff2html/bundles/js/diff2html-ui.min.js"></script>

Init

const targetElement = document.getElementById('destination-elem-id');
const configuration = { drawFileList: true, matching: 'lines' };

const diff2htmlUi = new Diff2HtmlUI(targetElement, diffString, configuration);
// or
const diff2htmlUi = new Diff2HtmlUI(targetElement, diffJson, configuration);

Draw

diff2htmlUi.draw();

Syntax Highlight

NOTE: The highlight.js css should come before the diff2html css

<!-- Stylesheet -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.13.1/styles/github.min.css" />
<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/diff2html/bundles/css/diff2html.min.css" />

<!-- Javascripts -->
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/diff2html/bundles/js/diff2html-ui.min.js"></script>

Pass the option highlight with value true or invoke diff2htmlUi.highlightCode() after diff2htmlUi.draw().

document.addEventListener('DOMContentLoaded', () => {
  const diffString = `diff --git a/sample.js b/sample.js
  index 0000001..0ddf2ba
  --- a/sample.js
  +++ b/sample.js
  @@ -1 +1 @@
  -console.log("Hello World!")
  +console.log("Hello from Diff2Html!")`;
  const targetElement = document.getElementById('myDiffElement');
  const configuration = { inputFormat: 'json', drawFileList: true, matching: 'lines', highlight: true };
  const diff2htmlUi = new Diff2HtmlUI(targetElement, diffString, configuration);
  diff2htmlUi.draw();
  diff2htmlUi.highlightCode();
});

Collapsable File Summary List

Add the dependencies.

<!-- Javascripts -->
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/diff2html/bundles/js/diff2html-ui.min.js"></script>

Invoke the Diff2HtmlUI helper Pass the option fileListToggle with value true or invoke diff2htmlUi.fileListToggle() after diff2htmlUi.draw().

document.addEventListener('DOMContentLoaded', () => {
  const targetElement = document.getElementById('myDiffElement');
  var diff2htmlUi = new Diff2HtmlUI(targetElement, lineDiffExample, { drawFileList: true, matching: 'lines' });
  diff2htmlUi.draw();
  diff2htmlUi.fileListToggle(false);
});

Diff2HtmlUI Examples

Example with plain HTML+CSS+JS

<!DOCTYPE html>
<html lang="en-us">
  <head>
    <meta charset="utf-8" />
    <!-- Make sure to load the highlight.js CSS file before the Diff2Html CSS file -->
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.7.1/styles/github.min.css" />
    <link
      rel="stylesheet"
      type="text/css"
      href="https://cdn.jsdelivr.net/npm/diff2html/bundles/css/diff2html.min.css"
    />
    <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/diff2html/bundles/js/diff2html-ui.min.js"></script>
  </head>
  <script>
    const diffString = `diff --git a/sample.js b/sample.js
      index 0000001..0ddf2ba
      --- a/sample.js
      +++ b/sample.js
      @@ -1 +1 @@
      -console.log("Hello World!")
      +console.log("Hello from Diff2Html!")`;

    document.addEventListener('DOMContentLoaded', function () {
      var targetElement = document.getElementById('myDiffElement');
      var configuration = {
        inputFormat: 'json',
        drawFileList: true,
        fileListToggle: false,
        fileListStartVisible: false,
        fileContentToggle: false,
        matching: 'lines',
        outputFormat: 'side-by-side',
        synchronisedScroll: true,
        highlight: true,
        renderNothingWhenEmpty: false,
      };
      var diff2htmlUi = new Diff2HtmlUI(targetElement, diffString, configuration);
      diff2htmlUi.draw();
      diff2htmlUi.highlightCode();
    });
  </script>
  <body>
    <div id="myDiffElement"></div>
  </body>
</html>

Diff2Html Usage

Diff2Html API

JSON representation of the diff

function parse(diffInput: string, configuration: Diff2HtmlConfig = {}): DiffFile[];

Pretty HTML representation of the diff

function html(diffInput: string | DiffFile[], configuration: Diff2HtmlConfig = {}): string;

Diff2Html Configuration

The HTML output accepts a Javascript object with configuration. Possible options:

• outputFormat: the format of the output data: 'line-by-line' or 'side-by-side', default is 'line-by-line'
• drawFileList: show a file list before the diff: true or false, default is true
• diffStyle: show differences level in each line: word or char, default is word
• diffMaxChanges: number of changed lines after which a file diff is deemed as too big and not displayed, default is undefined
• diffMaxLineLength: number of characters in a diff line after which a file diff is deemed as too big and not displayed, default is undefined
• diffTooBigMessage: function allowing to customize the message in case of file diff too big (if diffMaxChanges or diffMaxLineLength is set)
• matching: matching level: 'lines' for matching lines, 'words' for matching lines and words or 'none', default is none
• matchWordsThreshold: similarity threshold for word matching, default is 0.25
• matchingMaxComparisons: perform at most this much comparisons for line matching a block of changes, default is 2500
• maxLineSizeInBlockForComparison: maximum number os characters of the bigger line in a block to apply comparison, default is 200
• maxLineLengthHighlight: only perform diff changes highlight if lines are smaller than this, default is 10000
• renderNothingWhenEmpty: render nothing if the diff shows no change in its comparison: true or false, default is false
• compiledTemplates: object with previously compiled templates to replace parts of the html
• rawTemplates: object with raw not compiled templates to replace parts of the html

  For more information regarding the possible templates look into src/templates

Diff2Html Browser

Import the stylesheet and the library code.

To load correctly in the Browser you need to include the stylesheet in the final HTML.

<!-- CSS -->
<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/diff2html/bundles/css/diff2html.min.css" />

<!-- Javascripts -->
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/diff2html/bundles/js/diff2html.min.js"></script>

It will now be available as a global variable named Diff2Html.

document.addEventListener('DOMContentLoaded', () => {
  var diffHtml = Diff2Html.html('<Unified Diff String>', {
    drawFileList: true,
    matching: 'lines',
    outputFormat: 'side-by-side',
  });
  document.getElementById('destination-elem-id').innerHTML = diffHtml;
});

Diff2Html NPM / Node.js Library

const Diff2html = require('diff2html');
const diffJson = Diff2html.parse('<Unified Diff String>');
const diffHtml = Diff2html.html(diffJson, { drawFileList: true });
console.log(diffHtml);

Diff2Html Examples

Example with Angular

• Typescript

import * as Diff2Html from 'diff2html';
import { Component, OnInit } from '@angular/core';

export class AppDiffComponent implements OnInit {
  outputHtml: string;
  constructor() {
    this.init();
  }

  ngOnInit() {}

  init() {
    let strInput =
      '--- a/server/vendor/golang.org/x/sys/unix/zsyscall_linux_mipsle.go\n+++ b/server/vendor/golang.org/x/sys/unix/zsyscall_linux_mipsle.go\n@@ -1035,6 +1035,17 @@ func Prctl(option int, arg2 uintptr, arg3 uintptr, arg4 uintptr, arg5 uintptr) (\n \n // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n \n+func Pselect(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timespec, sigmask *Sigset_t) (n int, err error) {\n+\tr0, _, e1 := Syscall6(SYS_PSELECT6, uintptr(nfd), uintptr(unsafe.Pointer(r)), uintptr(unsafe.Pointer(w)), uintptr(unsafe.Pointer(e)), uintptr(unsafe.Pointer(timeout)), uintptr(unsafe.Pointer(sigmask)))\n+\tn = int(r0)\n+\tif e1 != 0 {\n+\t\terr = errnoErr(e1)\n+\t}\n+\treturn\n+}\n+\n+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n+\n func read(fd int, p []byte) (n int, err error) {\n \tvar _p0 unsafe.Pointer\n \tif len(p) > 0 {\n';
    let outputHtml = Diff2Html.html(strInput, { drawFileList: true, matching: 'lines' });
    this.outputHtml = outputHtml;
  }
}

• HTML

<!DOCTYPE html>
<html>
  <head>
    <title>diff2html</title>
  </head>
  <body>
    <div [innerHtml]="outputHtml"></div>
  </body>
</html>

• .angular-cli.json - Add styles

"styles": [
  "diff2html.min.css"
]

Example with Vue.js

<template>
  <div v-html="prettyHtml" />
</template>

<script>
import * as Diff2Html from 'diff2html';
import 'diff2html/bundles/css/diff2html.min.css';

export default {
  data() {
    return {
      diffs:
        '--- a/server/vendor/golang.org/x/sys/unix/zsyscall_linux_mipsle.go\n+++ b/server/vendor/golang.org/x/sys/unix/zsyscall_linux_mipsle.go\n@@ -1035,6 +1035,17 @@ func Prctl(option int, arg2 uintptr, arg3 uintptr, arg4 uintptr, arg5 uintptr) (\n \n // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n \n+func Pselect(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timespec, sigmask *Sigset_t) (n int, err error) {\n+\tr0, _, e1 := Syscall6(SYS_PSELECT6, uintptr(nfd), uintptr(unsafe.Pointer(r)), uintptr(unsafe.Pointer(w)), uintptr(unsafe.Pointer(e)), uintptr(unsafe.Pointer(timeout)), uintptr(unsafe.Pointer(sigmask)))\n+\tn = int(r0)\n+\tif e1 != 0 {\n+\t\terr = errnoErr(e1)\n+\t}\n+\treturn\n+}\n+\n+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT\n+\n func read(fd int, p []byte) (n int, err error) {\n \tvar _p0 unsafe.Pointer\n \tif len(p) > 0 {\n',
    };
  },
  computed: {
    prettyHtml() {
      return Diff2Html.html(this.diffs, {
        drawFileList: true,
        matching: 'lines',
        outputFormat: 'side-by-side',
      });
    },
  },
};
</script>

Troubleshooting

1. Out of memory or Slow execution

Causes:

• Big files
• Big lines

Fix:

• Disable the line matching algorithm, by setting the option {"matching": "none"} when invoking diff2html

Contribute

This is a developer friendly project, all the contributions are welcome. To contribute just send a pull request with your changes following the guidelines described in CONTRIBUTING.md. I will try to review them as soon as possible.

Contributors

Thanks goes to these wonderful people (emoji key):

Rodrigo Fernandes 💻	stockmind 💻	Ivan Vorontsov 💻	Nick Brewer 💻	Matt Wade 🐛	Rafael Cortês 💻	Nuno Teixeira 💻
Koki Oyatsu 🐛	James Monger 📖	Wessel van der Pal 🛡️	jk-kim 💻	Sergey Semenov 🐛	Nick Mitchell 🐛	Samir Aguiar 📖
pubkey 📖	Илья 📖	Mohamed Akram 🐛	Eugene Marcotte 💻	Dima Sabanin 🚧	Ben Abbott 📖	弘树@阿里 🐛
Mikko Rantanen 🐛	Ann 📖	escitalopram 🐛 💻	dependabot[bot] 🛡️ 🚧	Josh Goldberg 💻

This project follows the all-contributors specification. Contributions of any kind welcome!

License

Copyright 2014-present Rodrigo Fernandes. Released under the terms of the MIT license.

Thanks

This project is inspired in pretty-diff by Scott González.

---