本文執行個體講述了JS使用ajax方法擷取指定url的head資訊中指定欄位值的方法。分享給大家供大家參考。具體分析如下：
下面的JS代碼用來擷取ajax_info.txt的head資訊中的Last modified屬性，最後修改時間
<!DOCTYPE html><html><head><script>function loadXMLDoc(url){var xmlhttp;if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); }else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); }xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { document.getElementById('p1').innerHTML="Last modified: " + xmlhttp.getResponseHeader('Last-Modified'); } }xmlhttp.open("GET",url,true);xmlhttp.send();}</script></head><body><p id="p1">The getResponseHeader() function is used to return specific header information from a resource, like length, server-type, content-type, last-modified, etc.</p><button onclick="loadXMLDoc('ajax_info.txt')">Get "Last-Modified" information</button></body></html>
希望本文所述對大家的javascript程式設計有所協助。
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