javascript parsing json

Question

I have a problem with javascript, im calling an ajax method that returns this string:

{
 "ObjectResponse": {
 "Operation": "OK",
 "Response": "SUCCESS",
 "Message": "List of AAA Found",
 "List": [
 {
 "keySource": "gat\/images\/images_set\/apple.jpg",
 "idSiteKey": "1",
 "text": "Apple"
 },
 {
 "keySource": "gat\/images\/images_set\/cat.jpg",
 "idSiteKey": "2",
 "text": "Cat"
 },
 {
 "keySource": "gat\/images\/images_set\/coffee.jpg",
 "idSiteKey": "3",
 "text": "Coffee"
 },
 {
 "keySource": "gat\/images\/images_set\/dog.jpg",
 "idSiteKey": "4",
 "text": "Dog"
 },
 {
 "keySource": "gat\/images\/images_set\/horse.jpg",
 "idSiteKey": "5",
 "text": "Horse"
 },
 {
 "keySource": "gat\/images\/images_set\/police.jpg",
 "idSiteKey": "6",
 "text": "Police"
 },
 {
 "keySource": "gat\/images\/images_set\/tree.jpg",
 "idSiteKey": "7",
 "text": "Tree"
 }
 ]
 }
}

I assing the content in this way:

xhr.onreadystatechange = ensureReadiness; 
....
responseText = xhr.responseText;

If i try to parse it on javascript with:

response = JSON.parse(responseText);

if I acces a property such response.ObjectResponse.Operation I do get the right content.. but when I try to access the List it allways brakes

and if I try the same String but instead of calling the service I assign the content to a var it works I do can access the List

var myTemporalString ='{"ObjectResponse":{"Operation":"OK","Response":"SUCCESS","Message":"List of Keys Found","List":...';
response.JSON.parse(myTemporalString);

Any suggestion why this could be happening?

• bfavaretto: This responseText = xhr.responseText; shoud be done inside ensureReadiness. You can only use the response from there.
• David Wolever: It's definitely not related to the actual XHR response. What happens when you try to access the .List? What do you mean by "it breaks"?
• lanzz: You should probably post more code.
• The Alpha: List is an array of object so you should use List[0]['keySource'] to get the first object and List[1]['keySource'] for the second and so on.

Answer 1

You can try this way,

 xhr.onreadystatechange = function() {
 if (xhr.readyState == 4) {
 if (xhr.status == 200) {
 try{
 var mJsonData = JSON.parse(xhr.responseText);
 }catch(err){
 console.log(err);
 alert(err);
 return;
 }
 for(i=0;i<jsondata.ObjectResponse.List.length;i++){
 console.log(jsondata.ObjectResponse.List[i].text);
 console.log(jsondata.ObjectResponse.List[i].keySource);
 console.log(jsondata.ObjectResponse.List[i]. idSiteKey);
 }
 }
 }
 }

Answer 2

Use a loop!

var array = response.ObjectResponse.List;
var len = array.length;
for(i=0; i<len; i++) {
 //Use array[i] to access the list
 array[i].keySource
 array[i].idSiteKey
 array[i].text
}