dom-compare

NodeJS module to compare two DOM-trees

• DOM Comparison
  • Comparison options
    • Comments comparison
    • Whitespace comparison
  • Cli utility
• DOM Canonic Form

Works with Node.JS v0.10+

DOM Comparison

Consider two documents. Expected:

<document>
    <!-- comment -->
    <element attribute="10" attributeX="100">
        <text>  text content </text>
        <inner>
            <node />
        </inner>
    </element>
    <![CDATA[  cdata node]]>
</document>

and actual one:

<document>
    <element attribute="100">
        <text>text content</text>
        <inner />
        <inner2 />
    </element>
    <![CDATA[cdata node  ]]>
</document>

One can compare them, get the result (is them equals, or not), and get extended report (why them are different).

var compare = require('dom-compare').compare,
    reporter = require('dom-compare').GroupingReporter,
    expected = ..., // expected DOM tree
    actual = ..., // actual one
    result, diff, groupedDiff;

// compare to DOM trees, get a result object
result = compare(expected, actual);

// get comparison result
console.log(result.getResult()); // false cause' trees are different

// get all differences
diff = result.getDifferences(); // array of diff-objects

// differences, grouped by node XPath
groupedDiff = reporter.getDifferences(result); // object, key - node XPATH, value - array of differences (strings)

// string representation
console.log(reporter.report(result));

Diff-object has a following form:

{
    node: "/document/element",
    message: "Attribute 'attribute': expected value '10' instead of '100'";
}

By using GroupingReporter one can get a result of a following type

{
    '/document/element': [
        "Attribute 'attribute': expected value '10' instead of '100'",
        "Extra attribute 'attributeX'"
    ]    
}

Comparison options

Comparison function can take a third argument with options like this:

var options = {
    stripSpaces: true,
    compareComments: true,
    collapseSpaces: true,
    normalizeNewlines: true
};

result = compare(expected, actual, options);

Comments comparison

By default, all comments are ignored. Set compareComments options to true to compare them too.

Whitespace comparison

By default, all text nodes (text, CDATA, comments if enabled as mentioned above) compared with respect to leading, trailing, and internal whitespaces. Set stripSpaces option to true to automatically strip spaces in text and comment nodes. This option doesn't change the way CDATA sections is compared, they are always compared with respect to whitespaces. Set collapseSpaces option to true to automatically collapse all spaces in text and comment nodes. This option doesn't change the way CDATA sections is compared, they are always compared with respect to whitespaces. Set normalizeNewlines option to true to automatically normalize new line characters in text, comment, and CDATA nodes.

Cli utility

When installed globally with npm install -g dom-compare cli utility is available. See usage information and command-line options with domcompare --help

You can try it on bundled samples:

  $ cd samples
  $ domcompare -s ./expected.xml ./actual.xml
  Documents are not equal
  /document/element
      Attribute 'attribute': expected value '10' instead of '100'
      Attribute 'attributeX' is missed
      Extra element 'inner2'
  /document/element/inner
      Element 'node' is missed
  /document
      Expected CDATA value '  cdata node' instead of 'cdata node  '

DOM Canonic Form

Implemented as XMLSerializer interface

Simple rules

1. Every node (text, node, attribute) on a new line
2. Empty tags - in a short form
3. Node indent - 4 spaces, attribute indent - 2 spaces
4. Attributes are sorted alphabetically
5. Attribute values are serialized in double quotes

Consider the following XML-document...

<document>
  <element>DOM Compare</element>
  <emptyNode></emptyNode>
  <element attribute1="value" attribute2="value">
    <element>Text node</element>
  </element>
</document>

...and code snippet...

var canonizingSerializer = new (require('dom-compare').XMLSerializer)();
var doc = ...; // parse above document somehow 
console.log(canonizingSerializer.serializeToString(doc));

You'll receive the following output

<document>
    <element>
        DOM Compare
    </element>
    <emptyNode />
    <element
      attribute1="value"
      attribute2="value">
        <element>
            Text node
        </element>
    </element>
</document>