Source/WebInspectorUI/UserInterface/Base/DOMUtilities.js - WebKit - Git at Google

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  * Copyright (C) 2007, 2008, 2013 Apple Inc.  All rights reserved.
  * Copyright (C) 2008 Matt Lilek <webkit@mattlilek.com>
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  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.
  * 3.  Neither the name of Apple Inc. ("Apple") 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 APPLE AND ITS 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 APPLE OR ITS 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.
  */

 WI.roleSelectorForNode = function(node)
 {
     // This is proposed syntax for CSS 4 computed role selector :role(foo) and subject to change.
     // See http://lists.w3.org/Archives/Public/www-style/2013Jul/0104.html
     var title = "";
     var role = node.computedRole();
     if (role)
         title = ":role(" + role + ")";
     return title;
 };

 WI.linkifyAccessibilityNodeReference = function(node)
 {
     if (!node)
         return null;
     // Same as linkifyNodeReference except the link text has the classnames removed...
     // ...for list brevity, and both text and title have roleSelectorForNode appended.
     var link = WI.linkifyNodeReference(node);
     var tagIdSelector = link.title;
     var classSelectorIndex = tagIdSelector.indexOf(".");
     if (classSelectorIndex > -1)
         tagIdSelector = tagIdSelector.substring(0, classSelectorIndex);
     var roleSelector = WI.roleSelectorForNode(node);
     link.textContent = tagIdSelector + roleSelector;
     link.title += roleSelector;
     return link;
 };

 WI.linkifyNodeReference = function(node, options = {})
 {
     let displayName = node.displayName;
     if (!isNaN(options.maxLength))
         displayName = displayName.truncate(options.maxLength);

     let link = document.createElement("span");
     link.append(displayName);
     return WI.linkifyNodeReferenceElement(node, link, {...options, displayName});
 };

 WI.linkifyNodeReferenceElement = function(node, element, options = {})
 {
     element.setAttribute("role", "link");
     element.title = options.displayName || node.displayName;

     let nodeType = node.nodeType();
     if ((nodeType !== Node.DOCUMENT_NODE || node.parentNode) && nodeType !== Node.TEXT_NODE)
         element.classList.add("node-link");

     WI.bindInteractionsForNodeToElement(node, element, options);

     return element;
 };

 WI.bindInteractionsForNodeToElement = function(node, element, options = {}) {
     if (!options.ignoreClick) {
         element.addEventListener("click", (event) => {
             WI.domManager.inspectElement(node.id, {
                 initiatorHint: WI.TabBrowser.TabNavigationInitiator.LinkClick,
             });
         });
     }

     element.addEventListener("mouseover", (event) => {
         node.highlight();
     });

     element.addEventListener("mouseout", (event) => {
         WI.domManager.hideDOMNodeHighlight();
     });

     element.addEventListener("contextmenu", (event) => {
         let contextMenu = WI.ContextMenu.createFromEvent(event);
         WI.appendContextMenuItemsForDOMNode(contextMenu, node, options);
     });
 };

 function createSVGElement(tagName)
 {
     return document.createElementNS("http://www.w3.org/2000/svg", tagName);
 }

 WI.cssPath = function(node, options = {})
 {
     console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");
     if (node.nodeType() !== Node.ELEMENT_NODE)
         return "";

     let suffix = "";
     if (node.isPseudoElement()) {
         suffix = "::" + node.pseudoType();
         node = node.parentNode;
     }

     let components = [];
     while (node) {
         let component = WI.cssPathComponent(node, options);
         if (!component)
             break;
         components.push(component);
         if (component.done)
             break;
         node = node.parentNode;
     }

     components.reverse();
     return components.map((x) => x.value).join(" > ") + suffix;
 };

 WI.cssPathComponent = function(node, options = {})
 {
     console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");
     console.assert(!node.isPseudoElement());
     if (node.nodeType() !== Node.ELEMENT_NODE)
         return null;

     let nodeName = node.nodeNameInCorrectCase();

     // Root node does not have siblings.
     if (!node.parentNode || node.parentNode.nodeType() === Node.DOCUMENT_NODE)
         return {value: nodeName, done: true};

     if (options.full) {
         function getUniqueAttributes(domNode) {
             let uniqueAttributes = new Map;
             for (let attribute of domNode.attributes()) {
                 let values = [attribute.value];
                 if (attribute.name === "id" || attribute.name === "class")
                     values = attribute.value.split(/\s+/);
                 uniqueAttributes.set(attribute.name, new Set(values));
             }
             return uniqueAttributes;
         }

         let nodeIndex = 0;
         let needsNthChild = false;
         let uniqueAttributes = getUniqueAttributes(node);
         node.parentNode.children.forEach((child, i) => {
             if (child.nodeType() !== Node.ELEMENT_NODE)
                 return;

             if (child === node) {
                 nodeIndex = i;
                 return;
             }

             if (needsNthChild || child.nodeNameInCorrectCase() !== nodeName)
                 return;

             let childUniqueAttributes = getUniqueAttributes(child);
             let subsetCount = 0;
             for (let [name, values] of uniqueAttributes) {
                 let childValues = childUniqueAttributes.get(name);
                 if (childValues && values.size <= childValues.size && values.isSubsetOf(childValues))
                     ++subsetCount;
             }

             if (subsetCount === uniqueAttributes.size)
                 needsNthChild = true;
         });

         function selectorForAttribute(values, prefix = "", shouldCSSEscape = false) {
             if (!values || !values.size)
                 return "";
             values = Array.from(values);
             values = values.filter((value) => value && value.length);
             if (!values.length)
                 return "";
             values = values.map((value) => shouldCSSEscape ? CSS.escape(value) : value.escapeCharacters("\""));
             return prefix + values.join(prefix);
         }

         let selector = nodeName;
         selector += selectorForAttribute(uniqueAttributes.get("id"), "#", true);
         selector += selectorForAttribute(uniqueAttributes.get("class"), ".", true);
         for (let [attribute, values] of uniqueAttributes) {
             if (attribute !== "id" && attribute !== "class")
                 selector += `[${attribute}="${selectorForAttribute(values)}"]`;
         }

         if (needsNthChild)
             selector += `:nth-child(${nodeIndex + 1})`;

         return {value: selector, done: false};
     }

     let lowerNodeName = node.nodeName().toLowerCase();

     // html, head, and body are unique nodes.
     if (lowerNodeName === "body" || lowerNodeName === "head" || lowerNodeName === "html")
         return {value: nodeName, done: true};

     // #id is unique.
     let id = node.getAttribute("id");
     if (id)
         return {value: node.escapedIdSelector, done: true};

     // Find uniqueness among siblings.
     //   - look for a unique className
     //   - look for a unique tagName
     //   - fallback to nth-child()

     function classNames(node) {
         let classAttribute = node.getAttribute("class");
         return classAttribute ? classAttribute.trim().split(/\s+/) : [];
     }

     let nthChildIndex = -1;
     let hasUniqueTagName = true;
     let uniqueClasses = new Set(classNames(node));

     let siblings = node.parentNode.children;
     let elementIndex = 0;
     for (let sibling of siblings) {
         if (sibling.nodeType() !== Node.ELEMENT_NODE)
             continue;

         elementIndex++;
         if (sibling === node) {
             nthChildIndex = elementIndex;
             continue;
         }

         if (sibling.nodeNameInCorrectCase() === nodeName)
             hasUniqueTagName = false;

         if (uniqueClasses.size) {
             let siblingClassNames = classNames(sibling);
             for (let className of siblingClassNames)
                 uniqueClasses.delete(className);
         }
     }

     let selector = nodeName;
     if (lowerNodeName === "input" && node.getAttribute("type") && !uniqueClasses.size)
         selector += `[type="${node.getAttribute("type")}"]`;
     if (!hasUniqueTagName) {
         if (uniqueClasses.size)
             selector += node.escapedClassSelector;
         else
             selector += `:nth-child(${nthChildIndex})`;
     }

     return {value: selector, done: false};
 };

 WI.xpath = function(node)
 {
     console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");

     if (node.nodeType() === Node.DOCUMENT_NODE)
         return "/";

     let components = [];
     while (node) {
         let component = WI.xpathComponent(node);
         if (!component)
             break;
         components.push(component);
         if (component.done)
             break;
         node = node.parentNode;
     }

     components.reverse();

     let prefix = components.length && components[0].done ? "" : "/";
     return prefix + components.map((x) => x.value).join("/");
 };

 WI.xpathComponent = function(node)
 {
     console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");

     let index = WI.xpathIndex(node);
     if (index === -1)
         return null;

     let value;

     switch (node.nodeType()) {
     case Node.DOCUMENT_NODE:
         return {value: "", done: true};
     case Node.ELEMENT_NODE:
         var id = node.getAttribute("id");
         if (id)
             return {value: `//*[@id="${id}"]`, done: true};
         value = node.localName();
         break;
     case Node.ATTRIBUTE_NODE:
         value = `@${node.nodeName()}`;
         break;
     case Node.TEXT_NODE:
     case Node.CDATA_SECTION_NODE:
         value = "text()";
         break;
     case Node.COMMENT_NODE:
         value = "comment()";
         break;
     case Node.PROCESSING_INSTRUCTION_NODE:
         value = "processing-instruction()";
         break;
     default:
         value = "";
         break;
     }

     if (index > 0)
         value += `[${index}]`;

     return {value, done: false};
 };

 WI.xpathIndex = function(node)
 {
     // Root node.
     if (!node.parentNode)
         return 0;

     // No siblings.
     let siblings = node.parentNode.children;
     if (siblings.length <= 1)
         return 0;

     // Find uniqueness among siblings.
     //   - look for a unique localName
     //   - fallback to index

     function isSimiliarNode(a, b) {
         if (a === b)
             return true;

         let aType = a.nodeType();
         let bType = b.nodeType();

         if (aType === Node.ELEMENT_NODE && bType === Node.ELEMENT_NODE)
             return a.localName() === b.localName();

         // XPath CDATA and text() are the same.
         if (aType === Node.CDATA_SECTION_NODE)
             return aType === Node.TEXT_NODE;
         if (bType === Node.CDATA_SECTION_NODE)
             return bType === Node.TEXT_NODE;

         return aType === bType;
     }

     let unique = true;
     let xPathIndex = -1;

     let xPathIndexCounter = 1; // XPath indices start at 1.
     for (let sibling of siblings) {
         if (!isSimiliarNode(node, sibling))
             continue;

         if (node === sibling) {
             xPathIndex = xPathIndexCounter;
             if (!unique)
                 return xPathIndex;
         } else {
             unique = false;
             if (xPathIndex !== -1)
                 return xPathIndex;
         }

         xPathIndexCounter++;
     }

     if (unique)
         return 0;

     console.assert(xPathIndex > 0, "Should have found the node.");
     return xPathIndex;
 };
	/*
	* Copyright (C) 2011 Google Inc. All rights reserved.
	* Copyright (C) 2007, 2008, 2013 Apple Inc. All rights reserved.
	* Copyright (C) 2008 Matt Lilek <webkit@mattlilek.com>
	* Copyright (C) 2009 Joseph Pecoraro
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. 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.
	* 3. Neither the name of Apple Inc. ("Apple") 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 APPLE AND ITS 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 APPLE OR ITS 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.
	*/

	WI.roleSelectorForNode = function(node)
	{
	// This is proposed syntax for CSS 4 computed role selector :role(foo) and subject to change.
	// See http://lists.w3.org/Archives/Public/www-style/2013Jul/0104.html
	var title = "";
	var role = node.computedRole();
	if (role)
	title = ":role(" + role + ")";
	return title;
	};

	WI.linkifyAccessibilityNodeReference = function(node)
	{
	if (!node)
	return null;
	// Same as linkifyNodeReference except the link text has the classnames removed...
	// ...for list brevity, and both text and title have roleSelectorForNode appended.
	var link = WI.linkifyNodeReference(node);
	var tagIdSelector = link.title;
	var classSelectorIndex = tagIdSelector.indexOf(".");
	if (classSelectorIndex > -1)
	tagIdSelector = tagIdSelector.substring(0, classSelectorIndex);
	var roleSelector = WI.roleSelectorForNode(node);
	link.textContent = tagIdSelector + roleSelector;
	link.title += roleSelector;
	return link;
	};

	WI.linkifyNodeReference = function(node, options = {})
	{
	let displayName = node.displayName;
	if (!isNaN(options.maxLength))
	displayName = displayName.truncate(options.maxLength);

	let link = document.createElement("span");
	link.append(displayName);
	return WI.linkifyNodeReferenceElement(node, link, {...options, displayName});
	};

	WI.linkifyNodeReferenceElement = function(node, element, options = {})
	{
	element.setAttribute("role", "link");
	element.title = options.displayName \|\| node.displayName;

	let nodeType = node.nodeType();
	if ((nodeType !== Node.DOCUMENT_NODE \|\| node.parentNode) && nodeType !== Node.TEXT_NODE)
	element.classList.add("node-link");

	WI.bindInteractionsForNodeToElement(node, element, options);

	return element;
	};

	WI.bindInteractionsForNodeToElement = function(node, element, options = {}) {
	if (!options.ignoreClick) {
	element.addEventListener("click", (event) => {
	WI.domManager.inspectElement(node.id, {
	initiatorHint: WI.TabBrowser.TabNavigationInitiator.LinkClick,
	});
	});
	}

	element.addEventListener("mouseover", (event) => {
	node.highlight();
	});

	element.addEventListener("mouseout", (event) => {
	WI.domManager.hideDOMNodeHighlight();
	});

	element.addEventListener("contextmenu", (event) => {
	let contextMenu = WI.ContextMenu.createFromEvent(event);
	WI.appendContextMenuItemsForDOMNode(contextMenu, node, options);
	});
	};

	function createSVGElement(tagName)
	{
	return document.createElementNS("http://www.w3.org/2000/svg", tagName);
	}

	WI.cssPath = function(node, options = {})
	{
	console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");
	if (node.nodeType() !== Node.ELEMENT_NODE)
	return "";

	let suffix = "";
	if (node.isPseudoElement()) {
	suffix = "::" + node.pseudoType();
	node = node.parentNode;
	}

	let components = [];
	while (node) {
	let component = WI.cssPathComponent(node, options);
	if (!component)
	break;
	components.push(component);
	if (component.done)
	break;
	node = node.parentNode;
	}

	components.reverse();
	return components.map((x) => x.value).join(" > ") + suffix;
	};

	WI.cssPathComponent = function(node, options = {})
	{
	console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");
	console.assert(!node.isPseudoElement());
	if (node.nodeType() !== Node.ELEMENT_NODE)
	return null;

	let nodeName = node.nodeNameInCorrectCase();

	// Root node does not have siblings.
	if (!node.parentNode \|\| node.parentNode.nodeType() === Node.DOCUMENT_NODE)
	return {value: nodeName, done: true};

	if (options.full) {
	function getUniqueAttributes(domNode) {
	let uniqueAttributes = new Map;
	for (let attribute of domNode.attributes()) {
	let values = [attribute.value];
	if (attribute.name === "id" \|\| attribute.name === "class")
	values = attribute.value.split(/\s+/);
	uniqueAttributes.set(attribute.name, new Set(values));
	}
	return uniqueAttributes;
	}

	let nodeIndex = 0;
	let needsNthChild = false;
	let uniqueAttributes = getUniqueAttributes(node);
	node.parentNode.children.forEach((child, i) => {
	if (child.nodeType() !== Node.ELEMENT_NODE)
	return;

	if (child === node) {
	nodeIndex = i;
	return;
	}

	if (needsNthChild \|\| child.nodeNameInCorrectCase() !== nodeName)
	return;

	let childUniqueAttributes = getUniqueAttributes(child);
	let subsetCount = 0;
	for (let [name, values] of uniqueAttributes) {
	let childValues = childUniqueAttributes.get(name);
	if (childValues && values.size <= childValues.size && values.isSubsetOf(childValues))
	++subsetCount;
	}

	if (subsetCount === uniqueAttributes.size)
	needsNthChild = true;
	});

	function selectorForAttribute(values, prefix = "", shouldCSSEscape = false) {
	if (!values \|\| !values.size)
	return "";
	values = Array.from(values);
	values = values.filter((value) => value && value.length);
	if (!values.length)
	return "";
	values = values.map((value) => shouldCSSEscape ? CSS.escape(value) : value.escapeCharacters("\""));
	return prefix + values.join(prefix);
	}

	let selector = nodeName;
	selector += selectorForAttribute(uniqueAttributes.get("id"), "#", true);
	selector += selectorForAttribute(uniqueAttributes.get("class"), ".", true);
	for (let [attribute, values] of uniqueAttributes) {
	if (attribute !== "id" && attribute !== "class")
	selector += `[${attribute}="${selectorForAttribute(values)}"]`;
	}

	if (needsNthChild)
	selector += `:nth-child(${nodeIndex + 1})`;

	return {value: selector, done: false};
	}

	let lowerNodeName = node.nodeName().toLowerCase();

	// html, head, and body are unique nodes.
	if (lowerNodeName === "body" \|\| lowerNodeName === "head" \|\| lowerNodeName === "html")
	return {value: nodeName, done: true};

	// #id is unique.
	let id = node.getAttribute("id");
	if (id)
	return {value: node.escapedIdSelector, done: true};

	// Find uniqueness among siblings.
	// - look for a unique className
	// - look for a unique tagName
	// - fallback to nth-child()

	function classNames(node) {
	let classAttribute = node.getAttribute("class");
	return classAttribute ? classAttribute.trim().split(/\s+/) : [];
	}

	let nthChildIndex = -1;
	let hasUniqueTagName = true;
	let uniqueClasses = new Set(classNames(node));

	let siblings = node.parentNode.children;
	let elementIndex = 0;
	for (let sibling of siblings) {
	if (sibling.nodeType() !== Node.ELEMENT_NODE)
	continue;

	elementIndex++;
	if (sibling === node) {
	nthChildIndex = elementIndex;
	continue;
	}

	if (sibling.nodeNameInCorrectCase() === nodeName)
	hasUniqueTagName = false;

	if (uniqueClasses.size) {
	let siblingClassNames = classNames(sibling);
	for (let className of siblingClassNames)
	uniqueClasses.delete(className);
	}
	}

	let selector = nodeName;
	if (lowerNodeName === "input" && node.getAttribute("type") && !uniqueClasses.size)
	selector += `[type="${node.getAttribute("type")}"]`;
	if (!hasUniqueTagName) {
	if (uniqueClasses.size)
	selector += node.escapedClassSelector;
	else
	selector += `:nth-child(${nthChildIndex})`;
	}

	return {value: selector, done: false};
	};

	WI.xpath = function(node)
	{
	console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");

	if (node.nodeType() === Node.DOCUMENT_NODE)
	return "/";

	let components = [];
	while (node) {
	let component = WI.xpathComponent(node);
	if (!component)
	break;
	components.push(component);
	if (component.done)
	break;
	node = node.parentNode;
	}

	components.reverse();

	let prefix = components.length && components[0].done ? "" : "/";
	return prefix + components.map((x) => x.value).join("/");
	};

	WI.xpathComponent = function(node)
	{
	console.assert(node instanceof WI.DOMNode, "Expected a DOMNode.");

	let index = WI.xpathIndex(node);
	if (index === -1)
	return null;

	let value;

	switch (node.nodeType()) {
	case Node.DOCUMENT_NODE:
	return {value: "", done: true};
	case Node.ELEMENT_NODE:
	var id = node.getAttribute("id");
	if (id)
	return {value: `//*[@id="${id}"]`, done: true};
	value = node.localName();
	break;
	case Node.ATTRIBUTE_NODE:
	value = `@${node.nodeName()}`;
	break;
	case Node.TEXT_NODE:
	case Node.CDATA_SECTION_NODE:
	value = "text()";
	break;
	case Node.COMMENT_NODE:
	value = "comment()";
	break;
	case Node.PROCESSING_INSTRUCTION_NODE:
	value = "processing-instruction()";
	break;
	default:
	value = "";
	break;
	}

	if (index > 0)
	value += `[${index}]`;

	return {value, done: false};
	};

	WI.xpathIndex = function(node)
	{
	// Root node.
	if (!node.parentNode)
	return 0;

	// No siblings.
	let siblings = node.parentNode.children;
	if (siblings.length <= 1)
	return 0;

	// Find uniqueness among siblings.
	// - look for a unique localName
	// - fallback to index

	function isSimiliarNode(a, b) {
	if (a === b)
	return true;

	let aType = a.nodeType();
	let bType = b.nodeType();

	if (aType === Node.ELEMENT_NODE && bType === Node.ELEMENT_NODE)
	return a.localName() === b.localName();

	// XPath CDATA and text() are the same.
	if (aType === Node.CDATA_SECTION_NODE)
	return aType === Node.TEXT_NODE;
	if (bType === Node.CDATA_SECTION_NODE)
	return bType === Node.TEXT_NODE;

	return aType === bType;
	}

	let unique = true;
	let xPathIndex = -1;

	let xPathIndexCounter = 1; // XPath indices start at 1.
	for (let sibling of siblings) {
	if (!isSimiliarNode(node, sibling))
	continue;

	if (node === sibling) {
	xPathIndex = xPathIndexCounter;
	if (!unique)
	return xPathIndex;
	} else {
	unique = false;
	if (xPathIndex !== -1)
	return xPathIndex;
	}

	xPathIndexCounter++;
	}

	if (unique)
	return 0;

	console.assert(xPathIndex > 0, "Should have found the node.");
	return xPathIndex;
	};