What is the ajax like in XMLHttpRequest

本篇文章为大家展示了XMLHttpRequest中的ajax是怎样的，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

调用

function(Url) { var XML = new XMLHttpRequest(); XML.onreadystatechange = function() { if (XML.readyState == 4) { if (XML.status == 200) { //XML.responseText } else { //XML.statusText } } else { //数据加载中... } }; XML.open("GET",Url); XML.send(null);};

定义XMLHttpRequest 适应不同的浏览器

// IE supportif (window.ActiveXObject && !window.XMLHttpRequest){ window.XMLHttpRequest = function() { var msxmls = new Array('Msxml2.XMLHTTP.5.0','Msxml2.XMLHTTP.4.0','Msxml2.XMLHTTP.3.0','Msxml2.XMLHTTP','Microsoft.XMLHTTP'); for (var i = 0; i

< msxmls.length; i++) { try { return new ActiveXObject(msxmls[i]); } catch (e) { } } return null; };}// Opera supportif (window.opera && !window.XMLHttpRequest){ window.XMLHttpRequest = function() { this.readyState = 0; // 0=uninitialized,1=loading,2=loaded,3=interactive,4=complete this.status = 0; // HTTP status codes this.statusText = ''; this._headers = []; this._aborted = false; this._async = true; this._defaultCharset = 'ISO-8859-1'; this._getCharset = function() { var charset = _defaultCharset; var contentType = this.getResponseHeader('Content-type').toUpperCase(); val = contentType.indexOf('CHARSET='); if (val != -1) { charset = contentType.substring(val); } val = charset.indexOf(';'); if (val != -1) { charset = charset.substring(0, val); } val = charset.indexOf(','); if (val != -1) { charset = charset.substring(0, val); } return charset; }; this.abort = function() { this._aborted = true; }; this.getAllResponseHeaders = function() { return this.getAllResponseHeader('*'); }; this.getAllResponseHeader = function(header) { var ret = ''; for (var i = 0; i < this._headers.length; i++) { if (header == '*' || this._headers[i].h == header) { ret += this._headers[i].h + ': ' + this._headers[i].v + '\n'; } } return ret; }; this.getResponseHeader = function(header) { var ret = getAllResponseHeader(header); var i = ret.indexOf('\n'); if (i != -1) { ret = ret.substring(0, i); } return ret; }; this.setRequestHeader = function(header, value) { this._headers[this._headers.length] = {h:header, v:value}; }; this.open = function(method, url, async, user, password) { this.method = method; this.url = url; this._async = true; this._aborted = false; this._headers = []; if (arguments.length >

= 3) { this._async = async; } if (arguments.length > 3) { opera.postError('XMLHttpRequest.open() - user/password not supported'); } this.readyState = 1; if (this.onreadystatechange) { this.onreadystatechange(); } }; this.send = function(data) { if (!navigator.javaEnabled()) { alert("XMLHttpRequest.send() - Java must be installed and enabled."); return; } if (this._async) { setTimeout(this._sendasync, 0, this, data); } else { this._sendsync(data); } }; this._sendasync = function(req, data) { if (!req._aborted) { req._sendsync(data); } }; this._sendsync = function(data) { this.readyState = 2; if (this.onreadystatechange) { this.onreadystatechange(); } var url = new java.net.URL(new java.net.URL_(window.location.href), this.url); var conn = url.openConnection(); for (var i = 0; i < this._headers.length; i++) { conn.setRequestProperty(this._headers[i].h, this._headers[i].v); } this._headers = []; if (this.method == 'POST') { // POST data conn.setDoOutput(true); var wr = new java.io.OutputStreamWriter(conn.getOutputStream(), this._getCharset()); wr.write(data); wr.flush(); wr.close(); } // read response headers // NOTE: the getHeaderField() methods always return nulls for me :( var gotContentEncoding = false; var gotContentLength = false; var gotContentType = false; var gotDate = false; var gotExpiration = false; var gotLastModified = false; for (var i = 0; ; i++) { var hdrName = conn.getHeaderFieldKey(i); var hdrValue = conn.getHeaderField(i); if (hdrName == null && hdrValue == null) { break; } if (hdrName != null) { this._headers[this._headers.length] = {h:hdrName, v:hdrValue}; switch (hdrName.toLowerCase()) { case 'content-encoding': gotContentEncoding = true; break; case 'content-length' : gotContentLength = true; break; case 'content-type' : gotContentType = true; break; case 'date' : gotDate = true; break; case 'expires' : gotExpiration = true; break; case 'last-modified' : gotLastModified = true; break; } } } // try to fill in any missing header information var val; val = conn.getContentEncoding(); if (val != null && !gotContentEncoding) this._headers[this._headers.length] = {h:'Content-encoding', v:val}; val = conn.getContentLength(); if (val != -1 && !gotContentLength) this._headers[this._headers.length] = {h:'Content-length', v:val}; val = conn.getContentType(); if (val != null && !gotContentType) this._headers[this._headers.length] = {h:'Content-type', v:val}; val = conn.getDate(); if (val != 0 && !gotDate) this._headers[this._headers.length] = {h:'Date', v:(new Date(val)).toUTCString()}; val = conn.getExpiration(); if (val != 0 && !gotExpiration) this._headers[this._headers.length] = {h:'Expires', v:(new Date(val)).toUTCString()}; val = conn.getLastModified(); if (val != 0 && !gotLastModified) this._headers[this._headers.length] = {h:'Last-modified', v:(new Date(val)).toUTCString()}; // read response data var reqdata = ''; var stream = conn.getInputStream(); if (stream) { var reader = new java.io.BufferedReader(new java.io.InputStreamReader(stream, this._getCharset())); var line; while ((line = reader.readLine()) != null) { if (this.readyState == 2) { this.readyState = 3; if (this.onreadystatechange) { this.onreadystatechange(); } } reqdata += line + '\n'; } reader.close(); this.status = 200; this.statusText = 'OK'; this.responseText = reqdata; this.readyState = 4; if (this.onreadystatechange) { this.onreadystatechange(); } if (this.onload) { this.onload(); } } else { // error this.status = 404; this.statusText = 'Not Found'; this.responseText = ''; this.readyState = 4; if (this.onreadystatechange) { this.onreadystatechange(); } if (this.onerror) { this.onerror(); } } }; };}

// ActiveXObject emulation

if (!window.ActiveXObject && window.XMLHttpRequest){ window.ActiveXObject = function(type) { switch (type.toLowerCase()) { case 'microsoft.xmlhttp': case 'msxml2.xmlhttp': case 'msxml2.xmlhttp.3.0': case 'msxml2.xmlhttp.4.0': case 'msxml2.xmlhttp.5.0': return new XMLHttpRequest(); } return null; };}上述内容就是XMLHttpRequest中的ajax是怎样的，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注行业资讯频道。