Check if an element matches a CSS selector string

matchesSelector.js

HTMLElement.prototype.matchesSelector = function(selector) {
    var clonedElem = this.cloneNode();
    var docFrag = new DocumentFragment();
    docFrag.appendChild(clonedElem);
    return (docFrag.querySelectorAll(selector).length > 0);
};

/*
document.body.matchesSelector("body") // true
*/