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 --save

API

-   Diff.diffChars(oldStr, newStr[, options]) - diffs two blocks of
    text, comparing character by character.

    Returns a list of change objects (See below).

    Options

    -   ignoreCase: true to ignore casing difference. Defaults to false.

-   Diff.diffWords(oldStr, newStr[, options]) - diffs two blocks of
    text, comparing word by word, ignoring whitespace.

    Returns a list of change objects (See below).

    Options

    -   ignoreCase: Same as in diffChars.

-   Diff.diffWordsWithSpace(oldStr, newStr[, options]) - diffs two
    blocks of text, comparing word by word, treating whitespace as
    significant.

    Returns a list of change objects (See below).

-   Diff.diffLines(oldStr, newStr[, options]) - diffs two blocks of
    text, comparing line by line.

    Options

    -   ignoreWhitespace: true to ignore leading and trailing
        whitespace. This is the same as diffTrimmedLines
    -   newlineIsToken: true to treat newline characters as separate
        tokens. This allows for changes to the newline structure to
        occur independently of the line content and to be treated as
        such. In general this is the more human friendly form of
        diffLines and diffLines is better suited for patches and other
        computer friendly output.

    Returns a list of change objects (See below).

-   Diff.diffTrimmedLines(oldStr, newStr[, options]) - diffs two blocks
    of text, comparing line by line, ignoring leading and trailing
    whitespace.

    Returns a list of change objects (See below).

-   Diff.diffSentences(oldStr, newStr[, options]) - diffs two blocks of
    text, comparing sentence by sentence.

    Returns a list of change objects (See below).

-   Diff.diffCss(oldStr, newStr[, options]) - diffs two blocks of text,
    comparing CSS tokens.

    Returns a list of change objects (See below).

-   Diff.diffJson(oldObj, newObj[, options]) - diffs two JSON objects,
    comparing the fields defined on each. The order of fields, etc does
    not matter in this comparison.

    Returns a list of change objects (See below).

-   Diff.diffArrays(oldArr, newArr[, options]) - diffs two arrays,
    comparing each item for strict equality (===).

    Options

    -   comparator: function(left, right) for custom equality checks

    Returns a list of change objects (See below).

-   Diff.createTwoFilesPatch(oldFileName, newFileName, oldStr, newStr, oldHeader, newHeader) -
    creates a unified diff patch.

    Parameters:

    -   oldFileName : String to be output in the filename section of the
        patch for the removals
    -   newFileName : String to be output in the filename section of the
        patch for the additions
    -   oldStr : Original string value
    -   newStr : New string value
    -   oldHeader : Additional information to include in the old file
        header
    -   newHeader : Additional information to include in the new file
        header
    -   options : An object with options. Currently, only context is
        supported and describes how many lines of context should be
        included.

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

    Just like Diff.createTwoFilesPatch, but with oldFileName being equal
    to newFileName.

-   Diff.structuredPatch(oldFileName, newFileName, oldStr, newStr, oldHeader, newHeader, options) -
    returns an object with an array of hunk objects.

    This method is similar to createTwoFilesPatch, but returns a data
    structure suitable for further processing. Parameters are the same
    as createTwoFilesPatch. The data structure returned may look like
    this:

        {
          oldFileName: 'oldfile', newFileName: 'newfile',
          oldHeader: 'header1', newHeader: 'header2',
          hunks: [{
            oldStart: 1, oldLines: 3, newStart: 1, newLines: 3,
            lines: [' line2', ' line3', '-line4', '+line5', '\\ No newline at end of file'],
          }]
        }

-   Diff.applyPatch(source, patch[, options]) - applies a unified diff
    patch.

    Return a string containing new version of provided data. patch may
    be a string diff or the output from the parsePatch or
    structuredPatch methods.

    The optional options object may have the following keys:

    -   fuzzFactor: Number of lines that are allowed to differ before
        rejecting a patch. Defaults to 0.
    -   compareLine(lineNumber, line, operation, patchContent): Callback
        used to compare to given lines to determine if they should be
        considered equal when patching. Defaults to strict equality but
        may be overridden to provide fuzzier comparison. Should return
        false if the lines should be rejected.

-   Diff.applyPatches(patch, options) - applies one or more patches.

    This method will iterate over the contents of the patch and apply to
    data provided through callbacks. The general flow for each patch
    index is:

    -   options.loadFile(index, callback) is called. The caller should
        then load the contents of the file and then pass that to the
        callback(err, data) callback. Passing an err will terminate
        further patch execution.
    -   options.patched(index, content, callback) is called once the
        patch has been applied. content will be the return value from
        applyPatch. When it's ready, the caller should call
        callback(err) callback. Passing an err will terminate further
        patch execution.

    Once all patches have been applied or an error occurs, the
    options.complete(err) callback is made.

-   Diff.parsePatch(diffStr) - Parses a patch into structured data

    Return a JSON object representation of the a patch, suitable for use
    with the applyPatch method. This parses to the same structure
    returned by Diff.structuredPatch.

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

All methods above which accept the optional callback method will run in
sync mode when that parameter is omitted and in async mode when
supplied. This allows for larger diffs without blocking the event loop.
This may be passed either directly as the final parameter or as the
callback field in the options object.

Change Objects

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

-   value: Text content
-   added: True if the value was inserted into the new string
-   removed: True if 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');
    const Diff = require('diff');

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

    const diff = Diff.diffChars(one, other);

    diff.forEach((part) => {
      // green for additions, red for deletions
      // grey for common parts
      const 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>
    const one = 'beep boop',
        other = 'beep boob blah',
        color = '';
        
    let span = null;

    const diff = Diff.diffChars(one, other),
        display = document.getElementById('display'),
        fragment = document.createDocumentFragment();

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

    display.appendChild(fragment);
    </script>

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

Full online demo

Compatibility

jsdiff supports all ES3 environments with some known issues on IE8 and
below. Under these browsers some diff algorithms such as word diff and
others may fail due to lack of support for capturing groups in the split
operation.

License

See LICENSE.
