polyfill-service/polyfills/document.querySelector/polyfill.js

A polyfill combinator

(function (global) {
	var
	head = document.getElementsByTagName('head')[0];

	function getElementsByQuery(node, selector, one) {
		var
		generator = document.createElement(),
		id = 'qsa' + String(Math.random()).slice(3),
		style, elements;

		generator.innerHTML = 'x<style>' + selector + '{qsa:' + id + ';}';

		style = head.appendChild(generator.lastChild);

		elements = getElements(node, selector, one, id);

		head.removeChild(style);

		return one ? elements[0] : elements;
	}

	function getElements(node, selector, one, id) {
		var
		validNode = /1|9/.test(node.nodeType),
		childNodes = node.childNodes,
		elements = [],
		index = -1,
		childNode;

		if (validNode && node.currentStyle && node.currentStyle.qsa === id) {
			if (elements.push(node) && one) {
				return elements;
			}
		}

		while (childNode = childNodes[++index]) {
			elements = elements.concat(getElements(childNode, selector, one, id));

			if (one && elements.length) {
				return elements;
			}
		}

		return elements;
	}

	Document.prototype.querySelector = Element.prototype.querySelector = function querySelectorAll(selector) {
		return getElementsByQuery(this, selector, true);
	};

	Document.prototype.querySelectorAll = Element.prototype.querySelectorAll = function querySelectorAll(selector) {
		return getElementsByQuery(this, selector, false);
	};
})(this);