Javascript | Objects, Arrays and functions

I would recommend using the friend objects rather than getting them by id and name.

DATA = {"users": [{"friend_id":"62","name":"name","username":"admin","thumb":"images/avatar/thumb_7d41870512afee28d91.jpg","status":"HI4","isonline":""},{"friend_id":"66","name":"Another name","username":"regi","thumb":"images/avatar/thumb_d3fcc14e41c3a77aa712ae54.jpg","status":"Всем привет!","isonline":"avtbsl0a6dcelkq2bd578u1qt6"},{"friend_id":"2679","name":"My name","username":"Another","thumb":"images/avatar/thumb_41effb41eb1f969230.jpg","status":"","isonline":""}]}

// simple data store definition
Store = {items:{}};
NewStore = function(items){
    var store = Object.create(Store); 
    store.items = items || {}; 
    return store 
};
Store.put = function(id, item){this.items[id] = item;};
Store.get = function(id){ return this.items[id]; };
Store.remove = function(id){ delete this.items[id]; };
Store.clear = function(){ this.items = {}; };

// example
var chat = {
    data : {
        friends : NewStore()
    }
}

// after data loaded
chat.data.friends.clear();
for( var i = 0; i < DATA.users.length; i += 1 ){
    var user = DATA.users[i];
    chat.data.friends.put( user.friend_id, user );
}

getFriend = function(id){ return chat.data.friends.get( id ); }

var friend = getFriend(66);
console.log(friend.name);
console.log(friend.username);
console.log(friend.thumb);

You cannot .push() to an object. Objects are key => value mappings, so you need to use char.data.friends[somekey] = f.users[i];

If you really just want a list with numeric keys, make x5fastchat.data.friends an array: x5fastchat.data.friends = [];

However, since you want to be able to access the elements by friend_id, do the following:

onSuccess: function(f){
   x5fastchat.data.friends = {};
   for(var i=0; i< f.users.length;i++){
      chat.data.friends[f.users[i].friend_id] = f.users[i]
   }
}

get_data_by_id: function (what, friend_id) {
    obj[what] = chat.data.friends[friend_id][what];
}

Note the obj[what] instead of your original obj.what: When writing obj.what, what is handled like a string, so it's equal to obj['what'] - but since it's a function argument you want obj[what].

Take a look at the following code. You can simply copy paste it into an HTML file and open it. click "go" and you should see the result. let me know if I did not understand you correctly. :

<script>

myObj = { "field1" : { "key1a" : "value1a" }, "field2" : "value2" }


function go()
{

    findField(myObj, ["field2"])
    findField(myObj, ["field1","key1a"])
}


function findField( obj, fields)
{

    var myVal = obj;
    for ( var i in fields )
    {
        myVal = myVal[fields[i]]
    }

    alert("your value is [" + myVal + "]");

}
</script>


<button onclick="go()">Go</button>