JS 职责链模式

[zhongs]

AOP实现职责链

Function.prototype.after = function (fn) {
  const _this = this;
  return function () {
    const ret = _this.apply(this, arguments);
    if (ret === "nextSuccessor") {
      return fn.apply(this, arguments);
    }
    return ret;
  };
};

const order500 = function (orderType, pay, stock) {
  if (orderType === 1 && pay === true) {
    console.log("500元定金购买，得到100元优惠券");
  } else {
    return "nextSuccessor";
  }
};

const order200 = function (orderType, pay, stock) {
  if (orderType === 2 && pay === true) {
    console.log("200元定金购买，得到50元优惠券");
  } else {
    return "nextSuccessor";
  }
};

const orderNormal = function (orderType, pay, stock) {
  if (stock > 0) {
    console.log("普通购买，没有优惠券");
  } else {
    console.log("手机库存不足");
  }
};

const order = order500.after(order200).after(orderNormal);

order(1, true, 500);
order(1, false, 500);

异步职责链

const order500 = function (orderType, pay, stock) {
  if (orderType === 1 && pay === true) {
    console.log("500元定金购买，得到100元优惠券");
  } else {
    return "nextSuccessor";
  }
};

const order200 = function (orderType, pay, stock) {
  if (orderType === 2 && pay === true) {
    console.log("200元定金购买，得到50元优惠券");
  } else {
    return "nextSuccessor";
  }
};

const orderNext = function (orderType, pay, stock) {
  setTimeout(() => this.next(), 2 * 1000);
};

const orderNormal = function (orderType, pay, stock) {
  if (stock > 0) {
    console.log("普通购买，没有优惠券");
  } else {
    console.log("手机库存不足");
  }
};

const Chain = function (fn) {
  this.fn = fn;
  this.successor = null;
};

Chain.prototype.setNextSuccessor = function (successor) {
  return (this.successor = successor);
};

Chain.prototype.passRequest = function () {
  const ret = this.fn.apply(this, arguments);
  if (ret === "nextSuccessor") {
    return (
      this.successor &&
      this.successor.passRequest.apply(this.successor, arguments)
    );
  }
  return ret;
};

Chain.prototype.next = function () {
  return (
    this.successor &&
    this.successor.passRequest.apply(this.successor, arguments)
  );
};

const chainOrder500 = new Chain(order500);
const chainOrder200 = new Chain(order200);
const chainOrderNormal = new Chain(orderNormal);
const chainOrderNext = new Chain(orderNext);

chainOrder500
  .setNextSuccessor(chainOrder200)
  .setNextSuccessor(chainOrderNext)
  .setNextSuccessor(chainOrderNormal);

chainOrder500.passRequest(1, false, 0);

职责链

/**
 * 需求：
 *  orderType:
 *    1 500元订单用户
 *    2 200元订单用户
 *    3 普通购买用户
 *  pay:
 *    是否支付定金
 *  stock:
 *    针对orderType = 3的普通用户，其它用户不受限制
 */

const order500 = function(orderType, pay, stock) {
  if (orderType === 1 && pay === true) {
    console.log("500元定金购买，得到100元优惠券");
  } else {
    return "nextSuccessor";
  }
};

const order200 = function(orderType, pay, stock) {
  if (orderType === 2 && pay === true) {
    console.log("200元定金购买，得到50元优惠券");
  } else {
    return "nextSuccessor";
  }
};

const orderNormal = function(orderType, pay, stock) {
  if (stock > 0) {
    console.log("普通购买，没有优惠券");
  } else {
    console.log("手机库存不足");
  }
};

//包装函数
const Chain = function(fn) {
  this.fn = fn;
  this.successor = null;
};

Chain.prototype.setNextSuccessor = function(successor) {
  return (this.successor = successor);
};

Chain.prototype.passRequest = function() {
  const ret = this.fn.apply(this, arguments);
  if (ret === "nextSuccessor") {
    return (
      this.successor &&
      this.successor.passRequest.apply(this.successor, arguments)
    );
  }
  return ret;
};

//将三种订单包装成职责链的节点
const chainOrder500 = new Chain(order500);
const chainOrder200 = new Chain(order200);
const chainOrderNormal = new Chain(orderNormal);

//指定职责链顺序
chainOrder500
  .setNextSuccessor(chainOrder200)
  .setNextSuccessor(chainOrderNormal);

chainOrder500.passRequest(1, true, 500);
chainOrder500.passRequest(2, true, 500);
chainOrder500.passRequest(3, true, 500);
chainOrder500.passRequest(1, false, 0);