JavaScript scoping in jQuery

Question

    function getData(jsonAddress) {
      var data = new Array();
      var xhr = $.getJSON(jsonAddress, function(meas) {
        for (var i = 0; i < meas.length ; i++) {
          var dt = datetimeSplitter(meas[i].valuedate);
          data[i] = [Date.UTC(dt[0],dt[1]-1,dt[2],dt[3],dt[4],dt[5]),parseInt(meas[i].value,10)];
        };
      });
      alert(data);
    }

I would like to make the variable "data" available to the function getData so I can return it (in this case alert). I understood it is a problem of scope, and can be solved with closure. I understood also what is a closure, but definitely don't know the syntax for this specific case.

Answer 1

It's not a problem of scope, it's a problem of asynchronous callbacks.

You need to pass in a callback function to this method, in order to get the response of your getJSON() call.

Answer 2

$.getJSON(jsonAddress, function(meas)....是异步调用，即在调用回调函数（其中数据设置有响应值）之前将调用alert语句。 ，您将看到它具有正确的值。

Answer 3

如果您确实不能像以前建议的那样多次使用异步调用，则也可以使用（$ .ajax）[http://api.jquery.com/jQuery.ajax/]-$ .getJSON只是一个它的变体-使其同步-请注意，这不是建议的方法，因为在浏览器同步检索数据时，您的应用程序将被阻塞。