Internet Explorer, for the most part, implements MSXml 4.0 or higher. However that’s (obviously) a Microsoft technology, and the standard implementation doesn’t support XPath in the DOM.

In particular the selectNodes() and selectSingleNode() functions are of particular use when manipulating XML or the DOM. Using these functions you can parse an XPath expression and get a nodelist of elements in your DOM that match the expression.

The code below adds basic XPath parsing functionality to the DOM in Mozilla. (Thanks to km0ti0n)

// mozXPath - http://km0.la/js/mozXPath/
// km0ti0n@gmail.com
// Code licensed under Creative Commons Attribution-ShareAlike License
// http://creativecommons.org/licenses/by-sa/2.5/
if (document.implementation.hasFeature("XPath", "3.0")) {
	if ( typeof XMLDocument == "undefined" ) {
		XMLDocument = Document;
	}
	XMLDocument.prototype.selectNodes = function(cXPathString, xNode) {
		if ( !xNode ) { xNode = this; }
		var oNSResolver = this.createNSResolver(this.documentElement);
		var aItems = this.evaluate(cXPathString, xNode, oNSResolver, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
		var aResult = [];
		for ( var i = 0; i < aItems.snapshotLength; i++) {
			aResult[i] =  aItems.snapshotItem(i);
		}
		return aResult;
	}
	XMLDocument.prototype.selectSingleNode = function(cXPathString, xNode) {
		if( !xNode ) { xNode = this; }
		var xItems = this.selectNodes(cXPathString, xNode);
		if ( xItems.length > 0 ) { return xItems[0]; }
		else { return null; }
	}

	Element.prototype.selectNodes = function(cXPathString) {
		if (this.ownerDocument.selectNodes) {
			return this.ownerDocument.selectNodes(cXPathString, this);
		} else { throw "For XML Elements Only"; }
	}

	Element.prototype.selectSingleNode = function(cXPathString) {
		if (this.ownerDocument.selectSingleNode) {
			return this.ownerDocument.selectSingleNode(cXPathString, this);
		} else { throw "For XML Elements Only"; }
	}
}

It appears that Opera doesn’t have the XMLDocument object type, so, when using the XmlHttpRequest object the responseXML is in fact a Document object.

To get around this fact, we can use:

if ( typeof XMLDocument == "undefined" ) {
    XMLDocument = Document;
}

To use these new features, in either IE or Firefox, you can now simple call the functions as a method of the elements themselves… e.g.:

On the following XML Document:

    
      Some Content
    
    
      Some Content
    
    
      Some Content
    

For the XML sample above, you can use the following XPath to select all ContentNode‘s with their enabled attribute set to “true”:
//subnode[@enabled='true']/contentnode

So you would retrieve your XML Node List by executing the following JavaScript function:

//assume the variable xDOM is an XmlDocument object
//...that has been pre-loaded with the example XML
var nodeList = xDOM.selectNodes('//subnode[@enabled='true']/contentnode');
for each (var xNode in nodeList) {
    //do some operation...
}

This would perform some operation on each contentnode which is inside a subnode with it’s enabled property set to true.

NOTE: Be sure to double check your syntax, spelling and remember XML/XPath is CaseSensitive.

Unfortunately JavaScript doesn’t have this sort of thing built in, so here’s how to implement your own trim() functions (as well as ltrim() and rtrim()) in various ways depending on the level of backward compatibility you require.

trim() member functions

Use the code below to make trim a method of all Strings. Ordinarily you would place this code into a global JavaScript file that would be included in all your pages.

String.prototype.trim = function() {
    return this.replace(/^\s+|\s+$/g,"");
}

String.prototype.ltrim = function() {
    return this.replace(/^\s+/,"");
}

String.prototype.rtrim = function() {
    return this.replace(/\s+$/,"");
}

Examples using trim(), ltrim(), and rtrim() prototyped methods

var testString = " hello world ";
alert("#"+ testString.trim() +"#");
alert("#"+ testString.ltrim() +"#");
alert("#"+ testString.rtrim() +"#");

standalone JavaScript functions

If you’d prefer to use regular functions to return trimmed strings rather than modifying the String object using prototyping, then try the following code:

function trim(value) {
    return value.replace(/^\s+|\s+$/g,"");
}
function ltrim(value) {
    return value.replace(/^\s+/,"");
}
function rtrim(value) {
    return value.replace(/\s+$/,"");
}

Examples using trim(), ltrim(), and rtrim() functions

var testString = " hello world ";
alert("#"+ trim(testString) +"#");
alert("#"+ ltrim(testString) +"#");
alert("#"+ rtrim(testString) +"#");

Compatibility

The above functions require JavaScript 1.2+ and JScript 3.0+ as they are using Regular Expressions to work their magic. This pretty much covers all modern browsers (v4 and above of IE and opera, and all versions of Firefox).
If you require functions that will be compatible with very old browsers only supporting JavaScript 1.0 or there about, try using the following set of functions. These functions strip the following standard whitespace characters: space, tab, line feed, carriage return, and form feed. The IsWhitespace function checks if a character is whitespace.

function ltrim(str) {
    for(var k = 0;
        k < str.length && isWhitespace(str.charAt(k));
        k++);
    return str.substring(k, str.length);
}
function rtrim(str) {
    for(var j=str.length-1;
        j>=0 && isWhitespace(str.charAt(j));
        j--);
    return str.substring(0,j+1);
}
function trim(str) {
    return ltrim(rtrim(str));
}
function isWhitespace(charToCheck) {
    var whitespaceChars = " \t\n\r\f";
    return (whitespaceChars.indexOf(charToCheck) != -1);
}

e.g. http://www.yesjames.com/test.php?myparam=justatest
calling “gerURLParam(‘myparam’) will return “justatest”

function getURLParam(name) {
  name = name.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
  var pattern = "[\\?&]"+name+"=([^&#]*)";
  var regex = new RegExp(pattern);
  var aResult = regex.exec(window.location.href);
  if ( aResult == null ) {
    return "";
  } else {
    return aResult[1];
  }
}