无法从嵌套的Json数据检索数据

Question

in the following code, i was trying to extract data from json, and there was few errors occur, which i dont understand. In my previous post, someone mentioned that it was related to closure issues. Can anyone please explain why this issues still occur eventhough i already change the "var" to "let" in both for loop?

I would like to try the bind solution, but, i dont understand the steps. this is because i am referring to for loop array in json file.

function displayData(data) {
var json = JSON.parse(data);

alert (json.projects[0].task_data[1].taskName); //working

for (let i = 0; i < json.projects.length; i++) {

    $.ajax({ url: epridlist, method: 'GET' }).then(function (datas) {
          alert (json.projects[i].projName); //success load the value
    });

    for (let j = 0; j < json.projects[i].task_data.length; j++) { 
        $.ajax({url: tasklist,method: 'GET'}).then(function (data) 
        {alert (json.projects[i].task_data[j].taskName);});//success only on first row, next row value is undefined  
         alert (json.projects[0].task_data[1].taskName); //undefined          
    }
}
}

this is the json data

{"projects":[{"projName":"1","task_data":[{"taskName":"1","task_detail_data":[{"h_sun":"0.00","h_mon":"0.00","h_tue":"0.00","h_wed":"0.00","h_thu":"0.00","h_fri":"0.00","h_sat":"0.00"}]},[{"taskName":"2","task_detail_data":[{"h_sun":"0.00","h_mon":"0.00","h_tue":"0.00","h_wed":"0.00","h_thu":"0.00","h_fri":"0.00","h_sat":"0.00"}]}]]},{"projName":"2","task_data":[{"taskName":"3","task_detail_data":[{"h_sun":"0.00","h_mon":"0.00","h_tue":"0.00","h_wed":"0.00","h_thu":"0.00","h_fri":"0.00","h_sat":"0.00"}]}]}]}

Thanks

Answer 1

It seems your JSON data has inconsitant structure.

When viewing JSON in Json Viewer program first element of task_data is an object while the second is an array (see below picture):

Below line in your code will cause an issue:

json.projects[0].task_data[1].taskName

Answer 2

This problem occur here: json.projects[0].task_data[1].taskName you're triying to accede an object how does not exists. task_data array in the second position is an array, not an object. The soluction to your problem is use json.projects[i].task_data[0].taskName acceding to the object instead of the array.