詳解JavaScript鍊式呼叫計算器的範例程式碼

FluentCalculator.one.plus.two // 1 + 2 = 3
FluentCalculator.one.plus.two.plus.three.minus.one.minus.two.minus.four //  -1
FluentCalculator.one.plus.ten - 10 // 1 + 10 - 10 = 1

FluentCalculator.one.one // undefined,因为值不能调用值
FluentCalculator.one.plus.plus // undefined,操作不能连续调用

"use strict";

var num = ["zero","one","two","three","four","five","six","seven","eight","nine","ten"];

var oprs = {plus : "+",minus : "-",times : "*",pidedBy : "/"};

var Magic = {};
//状态对象，父对象
function Status(value,opr){
	//当前运算结果
    this.value = value;
	//当前操作符
    this.opr = opr;
}
//值状态对象，继承状态对象
function NumStatus(value,opr){
    Status.call(this,value,opr);
}
//操作状态对象，继承状态对象
function OprStatus(value,opr){
    Status.call(this,value,opr);
}
//给值状态对象原型上绑定方法
for(let i=0;i<num.length;i++){
    Object.defineProperty(Magic,num[i],{
        get : function(){  
            var val;
            if(!this.opr){
                val = i;
            }
            else{              
                switch(this.opr){
                    case "+":val = this.value + i;break;
                    case "-":val = this.value - i;break;
                    case "*":val = this.value * i;break;
                    case "/":val = this.value / i;break;
                }
            }
			//返回操作状态对象
            return new OprStatus(val,null);
        }
    });
}
//给操作状态对象原型上绑定方法
for(let i in oprs){
    if(oprs.hasOwnProperty(i)){
        Object.defineProperty(OprStatus.prototype,i,{
            get : function(){
				//返回值状态对象
                return new NumStatus(this.value,oprs[i]);
            }
        });
    }
}

var FluentCalculator = Magic;

NumStatus.prototype = Magic;
//所有调用结束时，就会调valueOf打印，直接返回最终运算结果
OprStatus.prototype.valueOf = function(){
    return this.value;
};