思路

• /ajax的get方式
  1.type:"get"
  2.url 寫在open函數(shù)里面船老，包含數(shù)據(jù)
  3.回調(diào)函數(shù)亲配，將處理得到的數(shù)據(jù)function（data）{操作},/

• *ajax的post方式 數(shù)據(jù)不能放在地址欄里面,所以要有data屬性缘眶，放在send函數(shù)里面發(fā)送
  1.type:"post"
  2.url
  3.data{
  diyigeshuju:
  diergeshuju:
  }
  4,回調(diào)函數(shù)
  */

• /ajax的跨域操作滑凉，JSONP淹遵。通過sccript標(biāo)簽發(fā)送api請求咽安，然后調(diào)用回調(diào)函數(shù)耕捞，得到數(shù)據(jù)
  1.type:"JSONP
  2.url
  3cab:(地址欄里面的key )
  4,回調(diào)函數(shù)/

代碼實現(xiàn)

$.ajax=function(options){
        var transp=window.ActiveXObject?new ActiveXObject():new XMLHttpRequest();
        switch(options.type){

            case "get":{
                transp.open("get",options.url,true);
                transp.onreadystatechange=function(){
                    if(transp.readyState==4){
                        if(transp.status==200||transp.status==304){
                            var msg=transp.responseText;
                            options.success(msg);//回調(diào)函數(shù)
                        }
                    }
                }
                transp.send();
                break;
            }
            case "post":{
                transp.open("post",options.url,true);
                transp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
                transp.onreadystatechange=function(){
                    if(transp.readyState==4){
                        if(transp.status==200||transp.status==304){
                            var msg=transp.responseText;
                            options.success(msg);
                        }
                    }
                }
                var str="";
                for(var arr in options.data){
                    str+=arr+"="+options.data[arr]+"&";
                }
                transp.send(str.substring(0,str,length-1));
                break;
            }
            case "JSONP":{
                var script=document.createElement("script");
                var name="_cbk"+parseInt(Math.random()*1000)+new Date().getTime();
                script.src=options.url+"&"+options.cab+"="+name;
                window[name]=function(data){
                    options.success(data);
                    script.remove();
                    delete window[name];
                }
                document.body.appendChild(script);
                break;
            }
        }
}