jQuery-如何使用每个循环遍历JSON

Question

I have cached the JSON returned from an Ajax call and need to loop through this to display it. I get the error, 'Cannot read property 'title' of undefined'. Can anyone help?

 $.each(cache['cat-'+cat], function(i, jd) {               
    var title= jd.title;  //issue is here
  )}

When I console.log(cache['cat-'+cat]) I get the below:

Object {
  date: "2016-07-28T15:08:03.596Z", 
  data: '[{"id":471,"title":"Lines and Calls","solution_areas":"lines-calls"}]'
}

When I console.log(jd) within the loop I get the below:

2016-07-28T15:13:14.553Z

if I use console.log(jd.data); I get

undefined

I have tried the below but they don't work either:

var title= jd.data.title;  
var title= jd.data[0].title;  

Can anyone tell me what I am doing wrong?

Answer 1

The way you are currently using it, each is going to iterate over every property of the cache['cat-'+cat] object, of which there are two, date and data .

So your anonymous function function(i, jd) will be called twice. The first time, jd will be the value of the date property (a string), the second time it will be the value of the data property (also a string, that happens to be formatted as JSON).

The contents of data need to be parsed before they can be accessed as an object/array, and given that data is formatted as an array, I am guessing that you actually want to iterate over that. Given the example provided, I would change it to:

$.each(JSON.parse(cache['cat-'+cat].data), function(i, jd) {               
    var title= jd.title;  
 });

Answer 2

You aren't accessing it properly. And since cache['cat-'+cat] is already the needed object, what's the purpose of $.each ? Should be

var title= JSON.parse(cache['cat-'+cat].data)[0].title;

(because the title is in the data , and the data is JSON).

Demo:

 var obj = { date: "2016-07-28T15:08:03.596Z", data: '[{"id":471,"title":"Lines and Calls","solution_areas":"lines-calls"}]' }; var title= JSON.parse(obj.data)[0].title; console.log(title); 

Answer 3

Just need to understand what is JSON and what is STRING

cache['cat-'+cat].data return a string that need to convert to JSON before pass to each loop:

var dataCacheReturned = cache['cat-'+cat];

var objCache = dataCacheReturned.data; //Its return a string 
objCache = JSON.parse(objCache); //Parse string to json

$.each(objCache, function(i, jd) {
  var title = jd.title; 
  console.log(title);
});