消除switch语句以获得更好的代码结构

• 代码演化1：纯switch

function counter(state = 0, action) {switch (action.type) {case 'INCREMENT':return state   1case 'DECREMENT':return state - 1default:return state}
}

• 用三元运算符代替

const counter = (state = 0, action) =>action.type === 'INCREMENT'   ? state   1: action.type === 'DECREMENT' ? state - 1: state

• 更换action.type ===，用对象本身的方法

function switchcase (cases, defaultCase, key) {if (cases.hasOwnProperty(key)) {return cases[key]} else {return defaultCase}
}

• 柯里化

const switchcase = cases => defaultCase => key =>cases.hasOwnProperty(key) ? cases[key] : defaultCaseconst counter = (state = 0, action) =>switchcase({'INCREMENT': state   1,'DECREMENT': state -1})(state)(action.type)

• 增加是否为函数检测

  const action = {type: 'INCREMENT'}const executeIfFunction = f =>f instanceof Function ? f() : fconst switchcase = cases => defaultCase => key =>cases.hasOwnProperty(key) ? cases[key] : defaultCaseconst switchcaseF = cases => defaultCase => key =>executeIfFunction(switchcase(cases)(defaultCase)(key))const counter = (state = 0, action) =>switchcaseF({'INCREMENT': () => state   1,'DECREMENT': () => state - 1})(state)(action.type)console.log(counter(0, action))

• switch应用--星期天转换

const switchcase = cases => defaultCase => key =>cases.hasOwnProperty(key) ? cases[key] : defaultCaseconst getDay = switchcase({0: 'Sunday',1: 'Monday',2: 'Tuesday',3: 'Wednesday',4: 'Thursday',5: 'Friday',6: 'Saturday'})('Unknown')const getCurrentDay = () => getDay(new Date().getDay())const day = getCurrentDay()

参考链接---消除switch获得更好的代码结构（英文文档-需翻墙）

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