JS设计模式-责任链模式

1.

看以下代码

function distributePrizes(payMethod, isPay, prizesCount) {
    //充值五百
    if (payMethod === 500) {
        if (isPay) {
            console.log("恭喜获得100块礼品卷");
        } else {
            if (prizesCount) {
                console.log("恭喜获得10块礼品卷");
            } else {
                console.log("抱歉，礼品券库存不足");
            }
        }
        //充值两百
    } else if (payMethod === 200) {
        if (isPay) {
            console.log("恭喜获得20块礼品卷");
        } else {
            if (prizesCount) {
                console.log("恭喜获得10块礼品卷");
            } else {
                console.log("抱歉，礼品券库存不足");
            }
        }
        //不充值
    } else {
        if (prizesCount) {
            console.log("恭喜获得10块礼品卷");
        } else {
            console.log("抱歉，礼品券库存不足");
        }
    }
}

各种嵌套的if-else if-else让人读起来很累。不难想象的是参数通过if-elseif-else不断的判断从而向下传递，那么可以采用责任链的模式（或者说链表）来进行优化,从而满足开放封闭原则(对拓展开放修改封闭)和单一职责原则

2.

function pay500(payMethod, isPay, prizesCount) {
    if (isPay && payMethod === 500) {
        console.log("恭喜获得100块礼品卷");
    } else {
        return "goNext";
    }
}
function pay200(payMethod, isPay, prizesCount) {
    if (isPay && payMethod === 200) {
        console.log("恭喜获得20块礼品卷");
    } else {
        return "goNext";
    }
}
function nexType(payMethod, isPay, prizesCount) {
    if (prizesCount) {
        console.log("恭喜获得10块礼品卷");
    } else {
        console.log("抱歉，礼品券库存不足");
    }
}
function testPayChain(fn){
    this.fn = fn
    this.nextChain = null
}
testPayChain.prototype.distributePrizes = function(){
    var mark = this.fn.apply(this,arguments)
    return mark === 'goNext' && this.nextChain.distributePrizes.apply(this.nextChain,arguments)
}
var head = new testPayChain(function(payMethod, isPay, prizesCount){return 'goNext'})
var chain500 = new testPayChain(pay500)
var chain200 = new testPayChain(pay200)
var chainNexType = new testPayChain(nexType)

head.nextChain = chain500
chain500.nextChain = chain200
chain200.nextChain = chainNexType

head.distributePrizes(500,true,500)
head.distributePrizes(200,true,500)
head.distributePrizes(500,false,500)
head.distributePrizes(200,false,0)

3.存在的问题

1.当链条很长的时候存在性能问题

2.当存在异步函数的时候即无法采用该方法