Javascript lets you have associative arrays (of sorts), e.g:

var myArray = {
    a : 'val1',
    b : 'val2'
};

If you want to loop over this array, you can use a foreach loop:

for( x in myArray ) {
    alert(myArray[x]);
}

This code will pop up a message box for each entry in the array. Because the key is assigned to the variable x, you can use the key as well as the value.