javascript - 尝试访问 json 对象时出现 'Cannot find variable' 错误

Question

希望有人能帮助我。下面的 JS 加载 JSON 文件并将县解析为选择菜单。它还会删除重复项。现在，在 JSON feed 中，每个项目都有这样的内容:

{
   "County":"Antrim",
   "Town":"Antrim Town",
   "Restaurant":"Diane's Restaurant & Pizzeria"
}

我想做的是在第一个选择菜单中，一旦用户选择了县，第二个选择菜单就会使用子对象中的值进行更新。目前我收到“找不到变量”错误，但我不知道原因。数据数组是否由于某种原因不可用？

<script type="text/JavaScript">
    $(document).ready(function(){
    //get a reference to the select elements
    var county = $('#county');
    var town = $('#town');
    var restaurant = $('#restaurant');

    //request the JSON data and parse into the select element
    $.getJSON('rai.json', function(data){
        console.log(data);

        //clear the current content of the select
        $('#county').html('');
        $('#county').append('<option>Please select county</option>');

        $('#county').html('');
        $('#town').append('<option>Please select town</option>');

        $('#restaurant').html('');
        $('#restaurant').append('<option>Please select restaurant</option>');

        //iterate over the data and append a select option
        $.each(data.irishtowns, function(key, val) {
            county.append('<option id="' + val.County + '">' + val.County+ '</option>');
        });

        var a = new Array();
        $('#county').children("option").each(function(x){
            test = false;
            b = a[x] = $(this).text();
            for (i=0;i<a.length-1;i++){
                if (b ==a[i]) test =true;
            }
            if (test) $(this).remove();
        });
    });

    $( "#county" ).change(function() {
        var myCounty = $(this).val();
        console.log(myCounty);
        $.each(data.irishtowns, function(key, val) {
            if (val.Town === myCounty) {
                town.append('<option id="' + val.Town + '">' + val.Town + '</option>');
            }
        });
    });
});
</script>

Answer 1

数据不在本行范围内

$.each(data.irishtowns, function(key, val) {

您可以将其移至回调中，或使用全局变量来提供访问:即在回调中包含一行 countries = data ，然后是

$.each(countries.irishtowns, function(key, val) {