Professional JavaScript For Web Developers

Chapter 15
for (var i=0; i < arrSignatures.length; i++) {
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);
oXmlDom.parseError = {
valueOf: function () { return this.errorCode; },
toString: function () { return this.errorCode.toString() }
};
oXmlDom.__initError__();
oXmlDom.addEventListener(“load”, function () {
this.__changeReadyState__(4);
}, false);
return oXmlDom;
}
} else {
throw new Error(“Your browser doesn’t support an XML DOM object.”);
}
This code uses object literal notation to create the parseError object in order to save space. The valueOf()
method is defined to return the errorCode property, which is the same as IE’s implementation; the
toString() method also returns the errorCode property, but as a string primitive. The initError()
method initializes all the parseError object’s properties. Here’s the code:
Document.prototype.__initError__ = function () {
this.parseError.errorCode = 0;
this.parseError.filepos = -1;
this.parseError.line = -1;
this.parseError.linepos = -1;
this.parseError.reason = null;
this.parseError.srcText = null;
this.parseError.url = null;
};
The next step is to check for a parsing error. This must be done in both the load() and loadXML() methods
because a parsing error can occur in either one. Because it’s bad coding practice to have the same code
in two places, it’s best to create a new method to handle parsing errors:
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