javascript中ajax的使用

1.json格式：{"naU":[{"number":"111","names":"pengpeng"}]}  a.txt

javascript代码：

 if (window.xmlhttprequest) {
                var xmlrequest = new window.xmlhttprequest();
            }
            else {
                var xmlrequest = new ActiveXObject("microsoft.xmlhttp");
            }
            var url = "a.txt?t=" + new Date().getDate();
            xmlrequest.open("GET", url, true);

            xmlrequest.onreadystatechange = function () {
                if (xmlrequest.readystate == 4 && xmlrequest.status == 200) {
                    var result = xmlrequest.responsetext;
                    var json = eval("("+result+")");
                    alert(json.naU[0].number)  //111
                    //alert(xmlrequest.responsetext+ "show");
                }
            }
            xmlrequest.send(null);

 2.  {"naU":[{"number":"V006","names":"LiLei"},{"number":"V007","names":"meimei"},{"number":"V008","names":"LiLei"}]}

使用$.ajax()方法实现：

                $.ajax({
                    type: "GET",
                   contentType:"application/json",
                    url:"aaa.txt",
                    dataType: 'json',
                    success: function (data) {
                        alert(data.naU[1].number);//Voo6
                        $("body").append("<div>" + data + "</div>").css("color","red");
                    },
                    error:function(){
                        alert("the function have a problem");
                    }
                })

3.使用$.get()方法获取：

     $.get("aaa.txt",function(data){    
                    var json =eval( "(" + data + ")");
                    $("body").append("<div>" + json.naU[1].number + "</div>").css("color", "red");//Voo7
                })
            })
//data还是json格式的字符串，需要用eval（）进行转换