ajax执行流程1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 /*  第一步创建ajax对象:     new XMLHttpRequest(); 第二步填写请求信息:     xhr.open('method',url,Asynchronous)     method(请求方式):         1、get通常用来获取数据,偶尔也会携带一些数据             (1)发送的内容显示在浏览器地址栏上。             (2)因为浏览器地址栏长度有限制,而get是通过url向服务器发送数据的,所以发送的数据大小会被限制。         2、post通常用来向服务器发送数据,偶尔也会携带一些数据到客户端。             (1)显示在请求头信息。             (2)post传输数据理论来说是没有大小限制的,post的大小限制来自于服务器。     url:请求文件的地址     Asynchronous(是否异步):         异步:不会等待数据请求结束继续执行下边的代码,当数据请求成功的时候,在回去进行处理。         同步:必须等待前边的数据请求结束才可以执行下一行代码,可能会造成页面假死。 第三步监控请求结果     ajax对象下边有一个onload在数据拿到之后就会触发     xhr.responseText表示请求到的文本内容。     xhr.responseXML表示请求到的XML。 第四步发送请求     xhr.send(data)     data发送给服务器的数据    * */ document.onclick=function(){     var xhr=new XMLHttpRequest();     xhr.open('get','1.txt',true);           xhr.onload=function(){         alert(xhr.responseText);     }     xhr.send(); }

例子

1 2 3 4 5 6 7 8 9 10 11 12 13 14 document.onclick = function(){     var xhr = new XMLHttpRequest();       xhr.open('get','php/data.xml',true);     xhr.onload = function(){         var entrys = xhr.responseXML.getElementsByTagName('entry');           for(var i=0;i<entrys.length;i++){             var names = entrys[i].getElementsByTagName('name')[0].innerHTML;             console.log(names);         }     };     xhr.send(); };
ajax执行流程1
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