Strings as keys of array

Question

When using strings as keys of an array, console is showing that the array without these declared values and while iterating by this values where keys are strin

Answer 1

In javascript there are 2 type of arrays: standard arrays and associative arrays

• [ ] - standard array - 0 based integer indexes only
• { } - associative array - javascript objects where keys can be any strings

So when you define:

var arr = [ 0, 1, 2, 3 ];

you are defining a standard array where indexes can only be integers. When you do arr["something"] since something (which is what you use as index) is not an integer you are basically defining a property to the arr object (everything is object in javascript). But you are not adding an element to the standard array.

Answer 2

for( var i = arr.length; i--; console.log( arr[ i ] ) );

This will only give you the numeric indices, of course, but you can still loop over both numeric indices and string keys of your array like this:

for (var x in arr) {
    console.log(x + ": " + arr[x]);
}
/* (console output):
     0: 0
     1: 1
     2: 2
     3: 3
     something: aught
*/