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
– connexo, Commented Nov 26, 2016 at 13:37
Because it is not loaded yet! your get_data() function did not the complete the request. so your arr is still empty — Tolgahan Albayrak
– Tolgahan Albayrak, Commented Nov 26, 2016 at 14:15

Max Koretskyi · Accepted Answer · 2016-11-26 13:38:07Z

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, 2016 at 13:38

answered Nov 26, 2016 at 13:32

Max Koretskyi

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4 Comments

Nick Over a year ago

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.

Max Koretskyi Over a year ago

@Nick, glad it helped. Good luck

Nick Over a year ago

rather than creating a new question I've updated it to show the scoping issues.

Max Koretskyi Over a year ago

@Nick, don't forget, you can accept my answer if gives you correct explanation

Thielicious · Accepted Answer · 2016-11-26 13:59:35Z

0

Just another option

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

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

answered Nov 26, 2016 at 13:59

Thielicious

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1 Comment

Nick Over a year ago

I've updated my question to show the scoping issues.

Lalitha · Accepted Answer · 2016-11-26 14:03:15Z

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, 2016 at 14:03

answered Nov 26, 2016 at 14:00

Lalitha

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2 Comments

Nick Over a year ago

I've updated my question to show the scoping issues.

Lalitha Over a year ago

Are you sure there is a scoping issue in your question? I get output 50 out of the block too!

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