Es6 函数式编程 MayBe函子的简单示例

初级函子的作用非常简单，使用场景主要体现在：深入访问object的属性的时候，不会担心由于属性不存在、undefined、null等问题出现异常。

MayBe.js

var MayBe = function (val) {

    this.value = val;

}

MayBe.of = function (val) {

    return new MayBe(val);

}

MayBe.prototype.isNothing = function () {

    return (this.value === null || this.value === undefined);

}

MayBe.prototype.map = function (fn) {

    return this.isNothing() ? MayBe.of(null) : MayBe.of(fn(this.value));

}

// demo1： MayBe?{value: "Mr. GOOGLE"}

MayBe.of('Google')

     .map(_ => _.toUpperCase())

     .map(_ => "Mr. " + _)

// demo2： MayBe?{value: null}

MayBe.of('Google')

     .map(_ => undefined)

     .map(_ => "Mr. " + _)