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initError

toString: function () { return this.errorCode.toString() }

};

oXmlDom.__initError__();

oXmlDom.addEventListener(“load”, function () {

this.__initError__();

this.__changeReadyState__(4);

}, false);

return oXmlDom;

} else {

throw new Error(“Your browser doesn’t support an XML DOM object.”);

}

Document.prototype.load = function (sURL) {

this.__initError__();

this.__changeReadyState__(1);

this.__load__(sURL);

};

Document.prototype.loadXML = function (sXml) {

this.__initError__();

this.__changeReadyState__(1);

var oParser = new DOMParser();

var oXmlDom = oParser.parseFromString(sXml, “text/xml”);

while (this.firstChild) {

this.removeChild(this.firstChild);

}

for (var i=0; i < oXmlDom.childNodes.length; i++) {

var oNewNode = this.importNode(oXmlDom.childNodes[i], true);

this.appendChild(oNewNode);

}

this.__checkForErrors__();

this.__changeReadyState__(4);

};

Notice that

initError()

is always called before the

readyState

is set to

. Likewise,

checkForErrors()

is always called just before

readyState

is set to

(which is why it must be called in the

onload

event

handler). These methods must called in order because

onreadystatechange

is called each time the

readyState

changes. If there is old data in the

parseError

object, it must be reset before

onreadystate-

change

is called, otherwise the old data could cause confusion. Along the same lines, the

parseError

object must contain the right data after

readyState

changes to

because all processing should be done

by then.

462

Chapter 15

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