Get value from object key inside JavaScript array

Question

Result of arr[0].price is 'undefined' outside of the function. Why is the variable arr not available when it is defined outside of the function and data is pushed to it?

var arr = [];

function get_data() {

    $.ajax({
      url: 'http://bitcoinprice.co.uk/site-options/',
      dataType: 'json',
      success: function(data) {
        var price = data['gbp_price'];
        var abs_change = data['gbp_abs_change'];
        var p_change = data['gbp_change'];
        var market_cap = data['gbp_market_cap'];
        var today_max = data['gbp_today_max'];
        var today_min = data['gbp_today_min'];

        var obj = {
            'price'      : 50,
            'abs_change' : abs_change,
            'p_change'   : p_change,
            'market_cap' : market_cap,
            'max'        : today_max,
            'min'        : today_min
        };

        arr.push(obj);
        console.log(arr[0].price); // 50
      }

    });

}
get_data();

console.log(arr[0].price) // Uncaught TypeError: Cannot read property 'price' of undefined(…)

I can't seem to find an answer to this. I am trying to get the value from the key 'price' outside of the function get_data().

I'm sure I'm missing something simple here.

Javascript has no associative arrays, only index-based arrays. — connexo, Nov 26 '16 at 13:37
@Nick, that's can't be true. Just open a console and run the code. It works. — Max Koretskyi, Nov 26 '16 at 13:45
Because it is not loaded yet! your get_data() function did not the complete the request. so your arr is still empty — Tolgahan Albayrak, Nov 26 '16 at 14:15
http://stackoverflow.com/questions/23667086/why-is-my-variable-unaltered-after-i-modify-it-inside-of-a-function-asynchron — trincot, Nov 26 '16 at 14:20

Max Koretskyi · Answer 1 · 2016-11-26T13:38:07.640

4

You need to use arr[0].price, because the price property is defined not on array, but on the object, that is the first entry in the array.

You code can be rewritten like that to demonstrate what's happening:

var o = {'price':price};
o.price; // 50
arr.push(o);
arr[0] === o; // true

You would have to do like this to actually assign a property to the array:

arr.price = price;

edited Nov 26 '16 at 13:38

answered Nov 26 '16 at 13:32

Max Koretskyi

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Ignore, your code works, as does mine. I simplified my issue and it eliminated some scope issues that are causing the problem. Thank you for your answer. – Nick Nov 26 '16 at 13:54
@Nick, glad it helped. Good luck – Max Koretskyi Nov 26 '16 at 13:57
rather than creating a new question I've updated it to show the scoping issues. – Nick Nov 26 '16 at 14:02
@Nick, don't forget, you can accept my answer if gives you correct explanation – Max Koretskyi Nov 27 '16 at 10:01

score 0 · Answer 2 · answered Nov 26 '16 at 13:59

0

Just another option

var price = 50,
        arr = [];
arr.price = price;

console.log(arr.price+'<br>'+arr['price']); // both return 50

answered Nov 26 '16 at 13:59

Thielicious

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I've updated my question to show the scoping issues. – Nick Nov 26 '16 at 14:02

Lalitha · Answer 3 · 2016-11-26T14:03:15.087

0

var arr is none other than array of objects. You just needed to loop in the array to get value.

var price = 50;
var arr = [];

var obj = {
    'price' : price
}

arr.push(obj);

for(var i of arr)
    {
    console.log(i['price']); //50
    }

edited Nov 26 '16 at 14:03

answered Nov 26 '16 at 14:00

Lalitha

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I've updated my question to show the scoping issues. – Nick Nov 26 '16 at 14:02
Are you sure there is a scoping issue in your question? I get output 50 out of the block too! – Lalitha Nov 26 '16 at 14:10

Get value from object key inside JavaScript array

3 Answers3