json - 轻量级图表加载json数据失败

Question

我正在使用轻量级图表，试图将数据分配到 testing.json

测试.json：

{"mydata":[{"time":"2020-10-27","value":"7.070"},{"time":"2020-10-28","value":"7.070"},{"time":"2020-10-30","value":"7.000"},{"time":"2020-11-02","value":"7.010"},{"time":"2020-11-05","value":"8.160"}]}

当使用这种方式读入轻量级图表时，它可以工作

$(document).ready(function () {
    $.getJSON("testing.json", 
        function (jsondata) {
            console.log(jsondata.mydata);
            areaSeries.setData( jsondata.mydata );
    });
 });

当使用这种方式直接声明而不读取json文件时，它也可以

var data = [
    {"time":"2020-10-27","value":"7.070"},
    {"time":"2020-10-28","value":"7.070"},
    {"time":"2020-10-30","value":"7.000"},
    {"time":"2020-11-02","value":"7.010"},
    {"time":"2020-11-05","value":"8.160"}
];
areaSeries.setData(data);

但是当单独分配给变量然后读入setData时，它失败了......

var data = [];
$(document).ready(function () {
    $.getJSON("testing.json", 
        function (jsondata) {
            console.log(jsondata.mydata);
            data= jsondata.mydata;
    });
});
areaSeries.setData(data);