jquery - 如何在ajax方法中为公共(public)变量设置值？

Question

这个问题已经有答案了:

How do I return the response from an asynchronous call? (42 个回答)

已关闭 7 年前。

我尝试在ajax方法的外部使用ajax的结果并编写此代码，但出现错误:

TypeError: foods is null    

for (var j = 0; j <foods.obj.length; j++) {

<小时/>

$(document).ready(function () {
            var foods = null;
            $.ajax({
                url: '/Train/TrianFood',
                data: { Tarrif: 1 },
                type: "POST",
                context: this,
                success: function (result) {foods = result;},
                error: function () {}
            });
            var parentOfFood = $('#accordion1 .person-information');
            for (var i = 0; i < parentOfFood.length; i++) {
                var foodSelect = $(parentOfFood[i]).find('select[name$=Food]');

                for (var j = 0; j <foods.obj.length; j++) {

                    foodSelect.append(new Option(foods.obj[j].ServiceType, foods.obj[j].ServiceTypeCode));
                }
            }
       });

如何解决这个问题？

Answer 1

这是因为loop在ajax响应回调之前执行。要解决此问题，请创建一个函数并在ajax响应后执行它。

尝试以下方式-

$(document).ready(function () {
    var foods = null;
    $.ajax({
        url: '/Train/TrianFood',
        data: { Tarrif: 1 },
        type: "POST",
        context: this,
        success: function (result) {
            foods = result;
            foodSelectHandler();
        },
        error: function () {}
    });
    var parentOfFood = $('#accordion1 .person-information');

    function foodSelectHandler(){
        for (var i = 0; i < parentOfFood.length; i++) {
            var foodSelect = $(parentOfFood[i]).find('select[name$=Food]');

            for (var j = 0; j <foods.obj.length; j++) {

                foodSelect.append(new Option(foods.obj[j].ServiceType, foods.obj[j].ServiceTypeCode));
            }
        }
    }

});