object each

HTML

<ul>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
</ul>

CSS

li {
    display: block;
    height: 90px;
    width: 200px;
    background: rgb(250,0,0);
    border: 1px solid #000;
    margin: 10px;
}

JavaScript

Object.prototype.each = function(callback) {
    var a = [];
    for (var i = 0; i < this.length; i++) {
        a[i] = this[i];
        callback(a[i]);
    }
}

var x = document.querySelectorAll('li');

x.each(function(elem) {
    elem.style.background = "black";
});