javascriptはxml解析xmlファイルを読みます.

function loadXML(xmlFile){
        var xmlDoc=null;
        //        
        //  IE   
        if(!window.DOMParser && window.ActiveXObject){
            var xmlDomVersions = ['MSXML.2.DOMDocument.6.0','MSXML.2.DOMDocument.3.0','Microsoft.XMLDOM'];
            for(var i=0;i<xmlDomVersions.length;i++){
                try{
                    xmlDoc = new ActiveXObject(xmlDomVersions[i]);
                    break;
                }catch(e){
                }
            }
        }
        //  Mozilla   
        else if(document.implementation && document.implementation.createDocument){
            try{
                /* document.implementation.createDocument('','',null);          
                 *                   URI    ； 
                 *                    ； 
                 *               （   doctype）
                 */
                xmlDoc = document.implementation.createDocument('','',null);
            }catch(e){
            }
        }
        else{
            return null;
        }

        if(xmlDoc!=null){
            xmlDoc.async = false;
            xmlDoc.load(xmlFile);
        }
        return xmlDoc;
}

function loadXMLStr(xmlString){
        var xmlDoc=null;
        //        
        //  IE    
        if(!window.DOMParser && window.ActiveXObject){   //window.DOMParser       ie   
            var xmlDomVersions = ['MSXML.2.DOMDocument.6.0','MSXML.2.DOMDocument.3.0','Microsoft.XMLDOM'];
            for(var i=0;i<xmlDomVersions.length;i++){
                try{
                    xmlDoc = new ActiveXObject(xmlDomVersions[i]);
                    xmlDoc.async = false;
                    xmlDoc.loadXML(xmlString); //loadXML    xml   
                    break;
                }catch(e){
                }
            }
        }
        //  Mozilla   
        else if(window.DOMParser && document.implementation && document.implementation.createDocument){
            try{
                /* DOMParser      XML         XML Document   。
                 *     DOMParser，                ，      parseFromString()   
                 * parseFromString(text, contentType)   text:     XML      contentType       
                 *     "text/xml" 、"application/xml"   "application/xhtml+xml"     。  ，    "text/html"。
                 */
                domParser = new  DOMParser();
                xmlDoc = domParser.parseFromString(xmlString, 'text/xml');
            }catch(e){
            }
        }
        else{
            return null;
        }

        return xmlDoc;
}

<script type="text/javascript">
window.onload = function(){
		var text = document.getElementById('aaa').value;
		var xmldoc=loadXMLStr(text);
		 var elements = xmldoc.getElementsByTagName("major");
		 for (var i = 0; i < elements.length; i++) {
			var value = elements[i].getElementsByTagName("class")[0].firstChild.nodeValue;
			alert(value);					
		}
	}
</script>

<textarea id="aaa">
<IS>
    <year time="2014">
        <major name="Computer Science">
            <class>1401</class>
            <class>1402</class>
            <class>1403</class>
            <class>1404</class>
        </major>
        <major name="Communication Engineering">
            <class>1405</class>
            <class>1406</class>
            <class>1407</class>
            <class>1408</class>
        </major>
    </year>
 
    <year time="2013">
        <major name="Computer Science">
            <class>1301</class>
            <class>1302</class>
            <class>1303</class>
            <class>1304</class>
        </major>
        <major name="Communication Engineering">
            <class>1305</class>
            <class>1306</class>
            <class>1307</class>
            <class>1308</class>
        </major>
    </year>
</IS>
</textarea>