index.js

(function(arr) {
	arr.forEach(function(item) {
		if (item.hasOwnProperty('before')) {
			return;
		}
		Object.defineProperty(item, 'before', {
			configurable: true,
			enumerable: true,
			writable: true,
			value: function before() {
				var argArr = Array.prototype.slice.call(arguments),
					docFrag = document.createDocumentFragment();

				argArr.forEach(function(argItem) {
					var isNode = argItem instanceof Node;
					docFrag.appendChild(
						isNode ? argItem : document.createTextNode(String(argItem))
					);
				});

				this.parentNode.insertBefore(docFrag, this);
			},
		});
	});
})([Element.prototype, CharacterData.prototype, DocumentType.prototype]);