Question

This Javascript logic puzzles me. I’m creating an array and setting the first element of it to a number. When I interate through it using a “for” loop Javascript turns the array key into a string. Why? I want it to stay a number.

stuff = [];
stuff[0] = 3;

for(var x in stuff) {
    alert(typeof x);
}

Answer 1

It’s because you’re looping through the array using for...in which is generally used for looping over properties of objects. The javascript engine is probably casting to a string because the string type is suitable for names of object properties.

Try this more traditional approach:

stuff = [];
stuff[0] = 3;

for(var i=0; i<stuff.length; i++) {
    var x = stuff[i];
    alert(typeof x);
}