javascript - 如何在 jquery 中访问 forEach 之外的值

Question

     GetMandatoryFieldsforUser: function (data) {
        var field = [];
        $.get("api/mapping/mandatoryfield?type=USER", function (data) {
            var self = this;
            self.dt = [];
            self.firmdata = JSON.parse(data.Data);
            console.log(self.firmdata);
            self.firmdata.forEach(function (item) {
                field.push(item.DisplayName);
            })
            console.log(field)   //able to print value                          
        })
        console.log(field) // not able to print value
       return MandatoryFields.User;
    },

EDIT

 MandatoryFields = {
    User: field,        
}

我的问题是我需要在 forEach 循环之外访问字段值。如何使用 jquery 或 javascript 实现这一点

EDIT

"api/mapping/mandatoryfield?type=USER" returns 

["First Name", "Last Name", "Location", "Email", "Password"],

查看已编辑的问题，我想在 MandatoryFields.User 中使用该字段数组，但如果我使用它，它不会显示值

Answer 1

这实现了 $.ajax:

GetMandatoryFieldsforUser: function (data) {
  var field = [];

  $.ajax({
    url: "api/mapping/mandatoryfield?type=USER"

  }).done(function(data) {
    // THIS PORTION IS EXECUTED AFTER DATA IS LOADED
    var self = this;
    self.dt = [];
    self.firmdata = JSON.parse(data.Data);
    console.log(self.firmdata);
    self.firmdata.forEach(function (item) {
      field.push(item.DisplayName);
    })
    console.log(field)

    /*
    USE return HERE!
    */
    return field; // OR SOMETHING ELSE

  })

  // THIS WON'T WORK, BECAUSE DATA IS RETRIEVED IN ASYNC!
  console.log(field) 
},