Ajax default is asynchronous request, if you want to $.ajax ({inside the global variable assignment, you need to sync operation, that is, add async:false, you can
Today, when I was working on a project, I ran into a problem. I'm using Ajax to assign a value to a global variable in $.ajax ({inside). The result is not worth, entangled for a half-day, and then online check, just know, AJAX default is asynchronous request, (when you want to assign value, this time the value did not get, so the assignment is not successful) if you want to be in $.ajax ({ The inside to the global variable assignment, need to change to sync operation, that is, plus async:false, it can be. The code is as follows: $.ajax ({type: "post", url: "A.action", data: {}, DataType: ' Text ', async:false,//set to synchronous operation can assign a value to global variable success success: function (data) {Usersname = Data;//usersname is a previously declared global variable}});