JavaScript 函数式编程之函子相关代码分享

一个简单的函子

// 一个简单的函子
class Container {constructor(value) {this._value = value}map(fn) {return new Container(fn(this._value))}
}// 简单使用
let r = new Container(3).map(v => v + 1).map(v => v * v)
console.log(r)

Maybe 函子

class MayBe {static of(value) {return new MayBe(value)}constructor(value) {this._value = value}map(fn) {return this.isNull() ? MayBe.of(null) : MayBe.of(fn(this._value))}isNull() {return this._value === null || this._value === undefined}
}// 对字符串做大写
let s1 = "hello world"
let s2 = nulllet r1 = MayBe.of(s1).map(v => v.toUpperCase())
console.log(r1)let r2 = MayBe.of(s2).map(v => v.toUpperCase())
console.log(r2)

Either 函子

class Left {static of(value) {return new Left(value)}constructor(value) {this._value = value}map(fn) {return this}
}class Right {static of(value) {return new Right(value)}constructor(value) {this._value = value}map(fn) {return Right.of(fn(this._value))}
}let r1 = Right.of(12).map(v => v + 1)
let r2 = Left.of(12).map(v => v + 1)console.log(r1)
console.log(r2)

IO 函子

const fp = require("lodash/fp")
class IO {static of(value){return new IO(()=>value)}constructor(fn) {this._value = fn}map(fn){return new IO(fp.flowRight(fn, this._value))}
}// 使用
let r = IO.of(process).map(p=>p.execPath)
console.log(r)console.log(r._value())