#js || callback functon example

callback.js

/* first */
JApp.GetUserIP(function(sIP) {
   oUserIp.val(sIP);
});


/* second */ 

that.GetUserIP = function(fnCallback) {
  var sDefault = "N/A";

  $.ajax({
    type: 'POST',
    url: '//api.userinfo.io/userinfos',
    success: function(sResponse) {
      var oResp = jQuery.parseJSON(sResponse);

      console.log(sResponse)

      if (oResp.ip_address != 'undefined') {
        fnCallback(oResp.ip_address);
      } else {
        fnCallback(sDefault);
      }
    },
    error: function() {
      fnCallback(sDefault);
    }
  });
}