Converting JavaScript object with numeric keys into array

There is nothing like a "JSON object" - JSON is a serialization notation.

If you want to transform your javascript object to a javascript array, either you write your own loop [which would not be that complex!], or you rely on underscore.js _.toArray() method:

var obj = {"0":"1","1":"2","2":"3","3":"4"};
var yourArray = _(obj).toArray();

It's actually very straight forward with jQuery's $.map

var arr = $.map(obj, function(el) { return el });

FIDDLE

and almost as easy without jQuery as well, converting the keys to an array and then mapping back the values with Array.map

var arr = Object.keys(obj).map(function(k) { return obj[k] });

FIDDLE

That's assuming it's already parsed as a javascript object, and isn't actually JSON, which is a string format, in that case a run through JSON.parse would be necessary as well.

In ES2015 there's Object.values to the rescue, which makes this a breeze

var arr = Object.values(obj);

You simply do it like

var data = {
    "0": "1",
    "1": "2",
    "2": "3",
    "3": "4"
};

var arr = [];
for (var prop in data) {
    arr.push(data[prop]);
}

console.log(arr);

DEMO

var json = '{"0":"1","1":"2","2":"3","3":"4"}';

var parsed = JSON.parse(json);

var arr = [];

for (var x in parsed) {
  arr.push(parsed[x]);
}

console.log(arr)

Hope this is what you're after!