xpath_util.js revision cedac228d2dd51db4b79ea1e72c7f249408ee061 
1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5/**
6 * @fileoverview A collection of JavaScript utilities used to simplify working
7 * with xpaths.
8 */
9
10
11goog.provide('cvox.XpathUtil');
12
13
14/**
15 * Utilities for simplifying working with xpaths
16 * @constructor
17 */
18cvox.XpathUtil = function() {
19 };
20
21
22/**
23 * Mapping for some default namespaces.
24 * @const
25 * @private
26 */
27cvox.XpathUtil.nameSpaces_ = {
28  'xhtml' : 'http://www.w3.org/1999/xhtml',
29  'mathml': 'http://www.w3.org/1998/Math/MathML'
30};
31
32
33/**
34 * Resolve some default name spaces.
35 * @param {string} prefix Namespace prefix.
36 * @return {string} The corresponding namespace URI.
37 */
38cvox.XpathUtil.resolveNameSpace = function(prefix) {
39  return cvox.XpathUtil.nameSpaces_[prefix] || null;
40};
41
42
43/**
44 * Given an XPath expression and rootNode, it returns an array of children nodes
45 * that match. The code for this function was taken from Mihai Parparita's GMail
46 * Macros Greasemonkey Script.
47 * http://gmail-greasemonkey.googlecode.com/svn/trunk/scripts/gmail-new-macros.user.js
48 * @param {string} expression The XPath expression to evaluate.
49 * @param {Node} rootNode The HTML node to start evaluating the XPath from.
50 * @return {Array} The array of children nodes that match.
51 */
52cvox.XpathUtil.evalXPath = function(expression, rootNode) {
53  try {
54    var xpathIterator = rootNode.ownerDocument.evaluate(
55      expression,
56      rootNode,
57      cvox.XpathUtil.resolveNameSpace,
58      XPathResult.ORDERED_NODE_ITERATOR_TYPE,
59      null); // no existing results
60  } catch (err) {
61    return [];
62  }
63  var results = [];
64  // Convert result to JS array
65  for (var xpathNode = xpathIterator.iterateNext();
66       xpathNode;
67       xpathNode = xpathIterator.iterateNext()) {
68    results.push(xpathNode);
69  }
70  return results;
71};
72
73/**
74 * Given a rootNode, it returns an array of all its leaf nodes.
75 * @param {Node} rootNode The node to get the leaf nodes from.
76 * @return {Array} The array of leaf nodes for the given rootNode.
77 */
78cvox.XpathUtil.getLeafNodes = function(rootNode) {
79  try {
80    var xpathIterator = rootNode.ownerDocument.evaluate(
81      './/*[count(*)=0]',
82      rootNode,
83      null, // no namespace resolver
84      XPathResult.ORDERED_NODE_ITERATOR_TYPE,
85      null); // no existing results
86  } catch (err) {
87    return [];
88  }
89  var results = [];
90  // Convert result to JS array
91  for (var xpathNode = xpathIterator.iterateNext();
92       xpathNode;
93       xpathNode = xpathIterator.iterateNext()) {
94    results.push(xpathNode);
95  }
96  return results;
97};
98
99/**
100 * Returns whether or not xpath is supported.
101 * @return {boolean} True if xpath is supported.
102 */
103cvox.XpathUtil.xpathSupported = function() {
104  if (typeof(XPathResult) == 'undefined') {
105    return false;
106  }
107  return true;
108};
109
110
111/**
112 * Given an XPath expression and rootNode, it evaluates the XPath expression as
113 * a boolean type and returns the result.
114 * @param {string} expression The XPath expression to evaluate.
115 * @param {Node} rootNode The HTML node to start evaluating the XPath from.
116 * @return {boolean} The result of evaluating the xpath expression.
117 */
118cvox.XpathUtil.evaluateBoolean = function(expression, rootNode) {
119  try {
120    var xpathResult = rootNode.ownerDocument.evaluate(
121        expression,
122        rootNode,
123        cvox.XpathUtil.resolveNameSpace,
124        XPathResult.BOOLEAN_TYPE,
125        null); // no existing results
126  } catch (err) {
127    return false;
128  }
129  return xpathResult.booleanValue;
130};
131
132
133/**
134 * Given an XPath expression and rootNode, it evaluates the XPath expression as
135 * a string type and returns the result.
136 * @param {string} expression The XPath expression to evaluate.
137 * @param {Node} rootNode The HTML node to start evaluating the XPath from.
138 * @return {string} The result of evaluating the Xpath expression.
139 */
140cvox.XpathUtil.evaluateString = function(expression, rootNode) {
141  try {
142    var xpathResult = rootNode.ownerDocument.evaluate(
143        expression,
144        rootNode,
145        cvox.XpathUtil.resolveNameSpace,
146        XPathResult.STRING_TYPE,
147        null); // no existing results
148  } catch (err) {
149    return '';
150  }
151  return xpathResult.stringValue;
152};
153