Method replaceChild

src/undom.js:62–68

(child, ref)

			return child;
		}
		replaceChild(child, ref) {
			if (ref.parentNode===this) {
				this.insertBefore(child, ref);
				ref.remove();
				return ref;
			}
		}
		removeChild(child) {
			splice(this.childNodes, child);
			return child;