Professional JavaScript For Web Developers

XML in JavaScript
try {
var oXmlDom = new ActiveXObject(arrSignatures[i]);
return oXmlDom;
}
} catch (oError) {
//ignore
}
throw new Error(“MSXML is not installed on your system.”);
} else if (document.implementation && document.implementation.createDocument) {
var oXmlDom = document.implementation.createDocument(“”,””,null);
return oXmlDom;
}
} else {
throw new Error(“Your browser doesn’t support an XML DOM object.”);
}
The next task is to make Mozilla support the readyState property and the onreadystatechange
event handler. This requires you to make some additional changes to the Document class.
First, add a readyState property and initialize it to 0.
Document.prototype.readyState = 0;
Next, create an onreadystatechange property and assign it the value of null:
Document.prototype.onreadystatechange = null;
Whenever the readyState property changes, the onreadystatechange function must be called. To
facilitate this, it’s best to create a method:
Document.prototype.__changeReadyState__ = function (iReadyState) {
this.readyState = iReadyState;
};
if (typeof this.onreadystatechange == “function”) {
this.onreadystatechange();
}
This method takes the new ready state as an argument and assigns it to the readyState property. Be
sure you check that onreadystatechange is actually a function before calling it (otherwise, this causes
an error). Because this method shouldn’t be called outside of the Document object, it uses the JavaScript
notation for a private method (leading and trailing double underscores).
Internet Explorer’s XML DOM supports five ready states, but there is no way to mimic all of them for
Mozilla. Really, the only important value for readyState is 4, which indicates that the XML DOM is
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