使用原生js实现ajax请求

使用原生js实现ajax请求

function createAjax(){
   var xmlObj;
   if (window.XMLHttpRequest) {
       xmlObj = new XMLHttpRequest();
   } else if (window.ActiveXObjext) {
       xmlObj = new ActiveXObject();
   }
   return xmlObj;
}

function sentAjax (url, fn, data) {
    var ajaxXml = createAjax();
    data ?  ajaxXml.open('POST', url, true) : ajaxXml.open('GET', url, true);
    ajaxXml.onreadystatechange = function () {
        if (ajaxXml.readyState == 4 && (ajaxXml.status == 200 || ajaxXml.status == 304)) {
            fn.call(this, ajaxXml.response);
        }
    }
    ajaxXml.setResponseHeader('Content-type','application/x-www-form-urlencoded');
    data ? ajaxXml.send(data) : ajaxXml.send(null);

}

Created with Raphaël 2.1.0 创建异步对象 创建一个新的http请求 发送数据 监听请求，返回response

* 下一节将重点讲ajax实现底层原理*