造个仓储系统 - 单例模式的应用 - 数据模型的建立 - [: '编程的套路 - JavaScript设计模式' |cut:tmp.cut_limit :]

/**
 * 仓库
 */
class Stock {
  constructor () {
    if (Stock.instance)
      return Stock.instance;
    else
      Stock.instance = this;

    this.sum   = 0;
    this.list  = [];
    this.maxId = 0;
  }

  /**
   * 入库
   * @param {Product} product
   */
  input (product) {
    product.id = this.generateId();
    this.sum += product.price;
    this.list.push(product);
  }

  /**
   * 出库
   * @param {number} id
   * @return {boolean}
   */
  output (id) {
    // 通过id找索引
    let index = this.list.findIndex(it => {
      return it.id === id;
    });

    if (index == -1)
      return false;

    // 减去总价
    this.sum -= this.list[ index ].price;
    // 删除产品
    this.list.splice(index, 1);
  }

  /**
   * 获取商品总价
   * @return {number}
   */
  getSum () {
    return this.sum;
  }

  /**
   * 获取商品总数
   * @return {number}
   */
  getTotal () {
    return this.list.length;
  }

  /**
   * 生成id
   * @return {number}
   */
  generateId () {
    return ++this.maxId;
  }

  /**
   * 获取所有商品
   * @return {Array}
   */
  all () {
    return this.list;
  }
}

/**
 * 产品
 */
class Product {
  constructor (type, price) {
    this.type  = type;
    this.price = price;
  }
}

let p1 = new Product('phone', 100);
let p2 = new Product('phone', 200);
let p3 = new Product('phone', 300);
let c1 = new Product('computer', 300);

let stock = new Stock();

stock.input(p1);
stock.input(p2);
stock.input(p3);
stock.input(c1);

console.log(stock.getSum());
console.log(stock.getTotal());

let stock2 = new Stock();

console.log(stock2 === stock);

stock2.output(2);

console.log(stock.getSum());
console.log(stock.getTotal());

console.log(stock.all());