[javascript] Add or change a value of JSON key with jquery or javascript

I have a JSON string(?) that I have returned from $.ajax() and named it data. Some of the values are empty and I need to add values to some of the keys and send it back to my PHP script.

I access the existing values by data.keyName. How do I add or change the values of certain keys in "data"?

This is what data looks like.

{
    "ID":"48",
    "userID":"0",
    "address":"750 North High Street",
    "city":"Columbus",
    "state":"OH",
    "zip":"43215",
    "lat":"39.977673",
    "lng":"-83.003357",
    "busNumber":"55",
    "isClaimed":"N",
    "whereFound":"",
    "busNum":"",
    "email":"",
    "fname":"",
    "lname":"",
    "comments":""
}  

It seems if your key is saved in a variable. data.key = value won't work.

You should use data[key] = value

Example:

data = {key1:'v1', key2:'v2'};

var mykey = 'key1'; 
data.mykey = 'newv1';
data[mykey] = 'newV2';

console.log(data);

Result:

{
  "key1": "newV2",
  "key2": "v2",
  "mykey": "newv1"
}

var y_axis_name=[];

 for(var point in jsonData[0].data)
              { 
                y_axis_name.push(point);

              }

y_axis_name is having all the key name

try on jsfiddle

data.userID = "10";

var temp = data.oldKey; // or data['oldKey']
data.newKey = temp;
delete data.oldKey;

Just like you would for any other variable, you just set it

alert(data.ID);
data.ID = "bar";  //dot notation 
alert(data.ID);    
data.userID = 123456;
data["address"] = "123 some street"; //bracket notation