diff

What is diff?

The diff npm package is a library that helps you compute differences between strings, such as characters or lines. It can be used to create patches, perform text comparisons, and highlight changes in a visual diff format. It is commonly used in version control systems, text editors, and any application that requires diffing functionality.

What are diff's main functionalities?

Character diff

This feature allows you to perform a character-by-character diff comparison between two strings. The result is an array of change objects indicating which characters have been added, removed, or remained unchanged.

"var diff = require('diff');\nvar diffResult = diff.diffChars('Hello World', 'Hello W0rld');\nconsole.log(diffResult);"

Word diff

This feature performs a word-by-word diff comparison, which is useful for comparing text with space-separated words. It provides a more granular view of changes than line diffs for prose or paragraphs.

"var diff = require('diff');\nvar diffResult = diff.diffWords('Hello World', 'Hello Planet');\nconsole.log(diffResult);"

Line diff

Line diff is used to compare text on a line-by-line basis. It's particularly useful for comparing code or any structured text where changes are often made in whole lines.

"var diff = require('diff');\nvar diffResult = diff.diffLines('line1\nline2', 'line1\nline3');\nconsole.log(diffResult);"

Creating patches

This feature allows you to create a unified diff patch which can be applied to a text file to transform it from one version to another. This is similar to the patches used in version control systems.

"var diff = require('diff');\nvar patch = diff.createPatch('file.txt', 'Hello World', 'Hello W0rld');\nconsole.log(patch);"

Applying patches

This feature applies a unified diff patch to a string, transforming it to the updated version. This is useful for updating text based on a set of changes.

"var diff = require('diff');\nvar patch = diff.createPatch('file.txt', 'Hello World', 'Hello W0rld');\nvar applied = diff.applyPatch('Hello World', patch);\nconsole.log(applied);"

Other packages similar to diff

jsdiff

jsdiff is an alias for the diff package. It provides the same functionality under a different name.

google-diff-match-patch

This package offers robust algorithms to perform the operations required for synchronizing plain text. It includes features like diff, match, and patch which are similar to those in diff, but with additional support for more complex operations and optimizations for speed.

jiff

jiff is a JSON diff and patch library that works with JSON objects instead of strings. It's useful for comparing and patching JSON structures, which is a different use case compared to the string-based operations of diff.

README

jsdiff

A javascript text differencing implementation.

Based on the algorithm proposed in "An O(ND) Difference Algorithm and its Variations" (Myers, 1986).

Installation

npm install diff

or

git clone git://github.com/kpdecker/jsdiff.git

API

• JsDiff.diffChars(oldStr, newStr) - diffs two blocks of text, comparing character by character.

  Returns a list of change objects (See below).

• JsDiff.diffWords(oldStr, newStr) - diffs two blocks of text, comparing word by word.

  Returns a list of change objects (See below).

• JsDiff.diffLines(oldStr, newStr) - diffs two blocks of text, comparing line by line.

  Returns a list of change objects (See below).

• JsDiff.diffCss(oldStr, newStr) - diffs two blocks of text, comparing CSS tokens.

  Returns a list of change objects (See below).

• JsDiff.createPatch(fileName, oldStr, newStr, oldHeader, newHeader) - creates a unified diff patch.

  Parameters:

  • fileName : String to be output in the filename sections of the patch
  • oldStr : Original string value
  • newStr : New string value
  • oldHeader : Additional information to include in the old file header
  • newHeader : Additional information to include in thew new file header

• JsDiff.applyPatch(oldStr, diffStr) - applies a unified diff patch.

  Return a string containing new version of provided data.

• convertChangesToXML(changes) - converts a list of changes to a serialized XML format

Change Objects

Many of the methods above return change objects. These objects are consist of the following fields:

• value: Text content
• added: True if the value was inserted into the new string
• removed: True of the value was removed from the old string

Note that some cases may omit a particular flag field. Comparison on the flag fields should always be done in a truthy or falsy manner.

Examples

Basic example in Node

require('colors')
var jsdiff = require('diff');

var one = 'beep boop';
var other = 'beep boob blah';

var diff = jsdiff.diffChars(one, other);

diff.forEach(function(part){
  // green for additions, red for deletions
  // grey for common parts
  var color = part.added ? 'green' :
    part.removed ? 'red' : 'grey';
  process.stderr.write(part.value[color]);
});

console.log()

Running the above program should yield

Basic example in a web page

<pre id="display"></pre>
<script src="diff.js"></script>
<script>
var one = 'beep boop';
var other = 'beep boob blah';

var diff = JsDiff.diffChars(one, other);

diff.forEach(function(part){
  // green for additions, red for deletions
  // grey for common parts
  var color = part.added ? 'green' :
    part.removed ? 'red' : 'grey';
  var span = document.createElement('span');
  span.style.color = color;
  span.appendChild(document
    .createTextNode(part.value));
  display.appendChild(span);
});
</script>

Open the above .html file in a browser and you should see

Full online demo

License

Software License Agreement (BSD License)

Copyright (c) 2009-2011, Kevin Decker [e-mail]

All rights reserved.

Redistribution and use of this software in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

• Neither the name of Kevin Decker nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.