Dúvida com javascript

dtmlXMLLoaderObject.prototype.loadXML = function(filePath) {
	try {
		this.xmlDoc = new XMLHttpRequest();
		this.xmlDoc.open("GET", filePath, true);
		this.xmlDoc.onreadystatechange = new this.waitLoadFunction(this);
		this.xmlDoc.send(null);
	} catch(e) {
		if (document.implementation && document.implementation.createDocument) {
			this.xmlDoc = document.implementation.createDocument("", "", null);
			this.xmlDoc.onload = new this.waitLoadFunction(this);
		} else {
			this.xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
			this.xmlDoc.async = "true";
			this.xmlDoc.onreadystatechange = new this.waitLoadFunction(this);
		}
		this.xmlDoc.load(filePath);
	}
};