Elements order in a “for (… in …)” loop

Question

Does the \"for…in\" loop in Javascript loop through the hashtables/elements in the order they are declared? Is there a browser which doesn\'t do it in order?
The object

Answer 1

This does not answer the question per se, but offers a solution to the basic problem.

Assuming that you cannot rely on order to preserved, why not use an array of objects with key and value as properties?

var myArray = [
    {
        'key'   : 'key1'
        'value' : 0
    },
    {
        'key'   : 'key2',
        'value' : 1
    } // ...
];

Now, it is up to you to ensure that the keys are unique (assuming that this is also important to you. As well, direct addressing changes, and for (...in...) now returns indexes as 'keys'.

> console.log(myArray[0].key);
key1

> for (let index in myArray) {console.log(myArray[index].value);}
0
1

See the Pen for (...in...) addressing in order by JDQ (@JDQ) on CodePen.