KnockoutJS Custom Binding: pointer

ko-pointer.js

/**
 * KO: Collects and cache pointers to elements.
 * @param {string|object} Binding value.
 * @config {string} The pointer's id.
 * @config {object}
 *     {obArray} [ob=pointers]
 *         Observable Array to store cache.
 *     {string} [id] The pointer's id.
 * @example
 * // View
 * <div data-bind="pointer: 'hello'"></div>
 * <div data-bind="pointer: 'world'"></div>
 * // ViewModel
 * pointers.get('hello'); // returns first div element
 */
ko.bindingHandlers.pointer = {
	init: function(element, valueAccessor, allBindingsAccessor, viewModel) {
		var value = valueAccessor();
		var pointers = (typeof value === 'object')
			? valueAccessor().ob
			: viewModel.pointers || (function() {
					viewModel.pointers = ko.observableArray();
					return viewModel.pointers;
				}());
		var id = (typeof value === 'object') ? value.id : value;
		
		if (!pointers.get) {
			pointers.get = function(id, i) {
				var i = i || 0;
				return this()[i] && (this()[i].id == id && this()[i].el || this.get(id, i+1));
			}
		}
		
		pointers.push({ id: id, el: element });
	}
}