JavaScript设计模式之责任链模式

适用场景：一个完整的流程，中间分成多个环节，各个环节之间存在一定的顺序关系，同时中间的环节的个数不一定，可能添加环节，也可能减少环节，只要保证顺序关系就可以。
如下图：

1. ES5写法

const Chain = function (fn) {
    this.fn = fn
    this.nextChain = null
    this.setNext = function (nextChain) {
        this.nextChain = nextChain
        return this.nextChain
    }
    this.run = function () {
        this.fn()
        this.nextChain && this.nextChain.run()
    }
}
//申请设备
const applyDevice = function () {
    console.log(111)
}
const chainApplyDevice = new Chain(applyDevice);
//选择收货地址
const selectAddress = function () {
    console.log(222)
}
const chainSelectAddress = new Chain(selectAddress);
//选择审核人
const selectChecker = function () {
    console.log(333)
}
const chainSelectChecker = new Chain(selectChecker);

chainApplyDevice.setNext(chainSelectAddress).setNext(chainSelectChecker);
chainApplyDevice.run(); //最后执行结果为111-222-333

2. ES6写法

class Chain {
   constructor(fn) {
       this.fn = fn
       this.nextChain = null
   }
   setNext (nextChain) {
       this.nextChain = nextChain
       return this.nextChain
   }
   run() {
       this.fn()
       this.nextChain && this.nextChain.run()
   }
}
//申请设备
const applyDevice = function () {
   console.log(111)
}
const chainApplyDevice = new Chain(applyDevice);
//选择收货地址
const selectAddress = function () {
   console.log(222)
}
const chainSelectAddress = new Chain(selectAddress);
//选择审核人
const selectChecker = function () {
   console.log(333)
}
const chainSelectChecker = new Chain(selectChecker);

chainApplyDevice.setNext(chainSelectAddress).setNext(chainSelectChecker);
chainApplyDevice.run(); //最后执行结果为111-222-333