for (var i = 0, c = this.length; i < c; i++) {
// делает свое дело
}
var divs = document.getElementsByTagName('div');
console.log(divs instanceof HTMLCollection); // true;
console.log(divs instanceof Array); // false;
divs = Array.prototype.slice.call(divs);
console.log(divs instanceof Array); // true;
var obj = {
1: '^',
2: '_',
3: '^',
length: 5
};
obj = Array.prototype.slice.call(obj);
console.log(obj); // [undefined, "^", "_", "^", undefined]
<script type="text/javascript">
document.write(unescape("%3Cscript src='http://pagead2.googlesyndication.com/pagead/show_ads.js' type='text/javascript'%3E%3C/script%3E"));
</script><script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"></script>