class Item { constructor(content, priority) { this.content = content; this.priority = priority; } } /** * The `ItemList` class collects items and then arranges them into an array * by priority. */ export default class ItemList { constructor() { /** * The items in the list. * * @type {Object} * @public */ this.items = {}; } /** * Check whether the list is empty. * * @returns {boolean} * @public */ isEmpty() { for (const i in this.items) { if(this.items.hasOwnProperty(i)) { return false; } } return true; } /** * Check whether an item is present in the list. * * @param key * @returns {boolean} */ has(key) { return !!this.items[key]; } /** * Get the content of an item. * * @param {String} key * @return {*} * @public */ get(key) { return this.items[key].content; } /** * Add an item to the list. * * @param {String} key A unique key for the item. * @param {*} content The item's content. * @param {Integer} [priority] The priority of the item. Items with a higher * priority will be positioned before items with a lower priority. * @public */ add(key, content, priority = 0) { this.items[key] = new Item(content, priority); } /** * Replace an item in the list, only if it is already present. * * @param {String} key * @param {*} [content] * @param {Integer} [priority] * @public */ replace(key, content = null, priority = null) { if (this.items[key]) { if (content !== null) { this.items[key].content = content; } if (priority !== null) { this.items[key].priority = priority; } } } /** * Remove an item from the list. * * @param {String} key * @public */ remove(key) { delete this.items[key]; } /** * Merge another list's items into this one. * * @param {ItemList} items * @public */ merge(items) { for (const i in items.items) { if (items.items.hasOwnProperty(i) && items.items[i] instanceof Item) { this.items[i] = items.items[i]; } } } /** * Convert the list into an array of item content arranged by priority. Each * item's content will be assigned an `itemName` property equal to the item's * unique key. * * @return {Array} * @public */ toArray() { const items = []; for (const i in this.items) { if (this.items.hasOwnProperty(i) && this.items[i] instanceof Item) { this.items[i].content = Object(this.items[i].content); this.items[i].content.itemName = i; items.push(this.items[i]); this.items[i].key = items.length; } } return items.sort((a, b) => { if (a.priority === b.priority) { return a.key - b.key; } else if (a.priority > b.priority) { return -1; } return 1; }).map(item => item.content); } }