jquery中ajax处理跨域的三大方式

 header("Access-Control-Allow-Origin:*"); /*星号表示所有的域都可以接受，*/ header("Access-Control-Allow-Methods:GET,POST");

 /*当前网址是localhost:3000*/ js代码  $.ajax({ type:"get", url:"http://localhost:3000/showAll",/*url写异域的请求地址*/ dataType:"jsonp",/*加上datatype*/ jsonpCallback:"cb",/*设置一个回调函数，名字随便取，和下面的函数里的名字相同就行*/ success:function(){ 。。。 } }); /*而在异域服务器上，*/ app.js app.get('/showAll',students.showAll);/*这和不跨域的写法相同*/   /*在异域服务器的showAll函数里，*/ var db = require("./database"); exports.showAll = function(req,res){ /**设置响应头允许ajax跨域访问**/ res.setHeader("Access-Control-Allow-Origin","*"); /*星号表示所有的异域请求都可以接受，*/ res.setHeader("Access-Control-Allow-Methods","GET,POST"); var con = db.getCon(); con.query("select * from t_students",function(error,rows){ if(error){ console.log("数据库出错："+error); }else{ /*注意这里，返回的就是jsonP的回调函数名+数据了*/ res.send("cb("+JSON.stringify(r)+")"); } }); }

//跨域（可跨所有域名）$.getJSON("http://user.hnce.com.cn/getregion.aspx?id=0&jsoncallback=?",function(json){ //要求远程请求页面的数据格式为： ?(json_data) //例如： //?([{"_name":"湖南省","_regionId":134},{"_name":"北京市","_regionId":143}]) alert(json[0]._name); }); $.getJSON("http://user.hnce.com.cn/getregion.aspx?id=0&jsoncallback=?",function(json){ //要求远程请求页面的数据格式为： ?(json_data) //例如： //?([{"_name":"湖南省","_regionId":134},{"_name":"北京市","_regionId":143}]) alert(json[0]._name); }); 

<script src="http://common.cnblogs.com/script/jquery.js" type="text/javascript"></script> <script type="text/javascript"> //跨域（可跨所有域名） $.getJSON("http://e.hnce.com.cn/tools/ajax.aspx?jsoncallback=?", { id: 0, action: 'jobcategoryjson' }, function(json) { alert(json[0].pid); alert(json[0].items[0]._name); });　  </script> 

<script src="http://common.cnblogs.com/script/jquery.js" type="text/javascript"></script> <script type="text/javascript"> //跨域（可跨所有域名） $.getJSON("http://e.hnce.com.cn/tools/ajax.aspx?jsoncallback=?", { id: 0, action: 'jobcategoryjson' }, function(json) { alert(json[0].pid); alert(json[0].items[0]._name); });　  </script> 

<script type="text/javascript" src="http://domain2.com/getjson?jsonp=parseResponse"> </script> 响应值：parseResponse({"Name": "Cheeso", "Rank": 7}) <script type="text/javascript" src="http://domain2.com/getjson?jsonp=parseResponse"> </script> 响应值：parseResponse({"Name": "Cheeso", "Rank": 7}) 

getJSON: function( url, data, callback ) { return jQuery.get(url, data, callback, "json"); }, 

 get: function( url, data, callback, type ) { // shift arguments if data argument was omited if ( jQuery.isFunction( data ) ) {  type = type || callback;  callback = data;  data = null; }  return jQuery.ajax({  type: "GET",  url: url,  data: data,  success: callback,  dataType: type });

 // Build temporary JSONP function if ( s.dataType === "json" && (s.data && jsre.test(s.data) || jsre.test(s.url)) ) { jsonp = s.jsonpCallback || ("jsonp" + jsc++);  // Replace the =? sequence both in the query string and the data if ( s.data ) { s.data = (s.data + "").replace(jsre, "=" + jsonp + "$1"); }  s.url = s.url.replace(jsre, "=" + jsonp + "$1");  // We need to make sure // that a JSONP style response is executed properly s.dataType = "script";  // Handle JSONP-style loading window[ jsonp ] = window[ jsonp ] || function( tmp ) { data = tmp; success(); complete(); // Garbage collect window[ jsonp ] = undefined;  try {  delete window[ jsonp ]; } catch(e) {}  if ( head ) {  head.removeChild( script ); } }; }  if ( s.dataType === "script" && s.cache === null ) { s.cache = false; }  if ( s.cache === false && type === "GET" ) { var ts = now();  // try replacing _= if it is there var ret = s.url.replace(rts, "$1_=" + ts + "$2");  // if nothing was replaced, add timestamp to the end s.url = ret + ((ret === s.url) ? (rquery.test(s.url) ? "&" : "?") + "_=" + ts : ""); } // If data is available, append data to url for get requests if ( s.data && type === "GET" ) { s.url += (rquery.test(s.url) ? "&" : "?") + s.data; }  // Watch for a new set of requests if ( s.global && ! jQuery.active++ ) { jQuery.event.trigger( "ajaxStart" ); }  // Matches an absolute URL, and saves the domain var parts = rurl.exec( s.url ), remote = parts && (parts[1] && parts[1] !== location.protocol || parts[2] !== location.host);  // If we're requesting a remote document // and trying to load JSON or Script with a GET if ( s.dataType === "script" && type === "GET" && remote ) { var head = document.getElementsByTagName("head")[0] || document.documentElement; var script = document.createElement("script"); script.src = s.url; if ( s.scriptCharset ) { script.charset = s.scriptCharset; }  // Handle Script loading if ( !jsonp ) { var done = false;  // Attach handlers for all browsers script.onload = script.onreadystatechange = function() {  if ( !done && (!this.readyState ||  this.readyState === "loaded" || this.readyState === "complete") ) {  done = true;  success();  complete();   // Handle memory leak in IE  script.onload = script.onreadystatechange = null;  if ( head && script.parentNode ) {  head.removeChild( script );  }  } }; }  // Use insertBefore instead of appendChild to circumvent an IE6 bug. // This arises when a base node is used (#2709 and #4378). head.insertBefore( script, head.firstChild );  // We handle everything using the script element injection return undefined; }