Question

I’m new to JavaScript, and I’m currently learning about the so-called for... in loop.

Does one actually use those loops when coding in JavaScript?

I can see how all other types of loops are useful — but not this one.

Someone shed some light on this please and include a real life example if possible.

Answer 1

In Javascript only Array objects can be iterated with a normal for(;;) loop. The for..in is used for enumeration of non-array objects:

for (var i in obj) {
    if (obj.hasOwnProperty(i)) { // if you don't want to access prototype properties
        alert(i);
        alert(obj[i]);
    }
}