Array.prototype.map()

gistfile1.js

// iterating through a collection of elements returned by querySelectorAll
var elems = document.querySelectorAll('select option:checked');
var values = [].map.call(elems, function(obj) {
    return obj.value;
});

// reverse a string
var str = '12345';
[].map.call(str, function(x) {
    return x;
}).reverse().join('');