Question

JS问题：这个变量分明已经指定，为什么alert提示没有定义？谢谢

$.ajax({

url: url,
type: "POST",
contentType: "application/json;utf-8",
dataType: 'json',
cache: false,
beforeSend:function(){
$("#content").html("正在请求数据,请稍后...");
},
success: function(data) {
//处理json
d=JSON.stringify(data);
},
error: function(data) {
alert(data);
}
});

alert(d);

Answer 1

ajax是异步执行，当alert(d)时，d还不存在，只有当ajax回调完成执行success时候才存在，可以添加async：false测试出来

Answer 2

hey ,man!
are you sure it was night??
it is noon ,ok?
about the question !i agree with the advice downstairs!

Answer 3

Hello guys, you must know that ajax is an Object with inner functions, so if you alert below it, it must be null or undefined!

Goodnight !

追问

I should now how to do. .Thinks..

追答

I thought you can define d above it all, and then you use d into success function, if success, then d will be well