__defineGetter__和__defineSetter__在日期中的应用

let { log } = console;

Date.prototype.__defineGetter__(‘year‘, function() {return this.getFullYear();});  
Date.prototype.__defineSetter__(‘year‘, function(y) {this.setFullYear(y)});  
Date.prototype.__defineGetter__(‘month‘, function() {return this.getMonth() + 1;});  
Date.prototype.__defineSetter__(‘month‘, function(m) {this.setMonth(m-1)});  
Date.prototype.__defineGetter__(‘day‘, function() {return this.getDate();});  
Date.prototype.__defineSetter__(‘day‘, function(d) {this.setDate(d)});    
Date.prototype.__defineGetter__(‘hour‘, function() {return this.getHours();});  
Date.prototype.__defineSetter__(‘hour‘, function(h) {this.setHours(h)});    
Date.prototype.__defineGetter__(‘minute‘, function() {return this.getMinutes();});  
Date.prototype.__defineSetter__(‘minute‘, function(m) {this.setMinutes(m)});    
Date.prototype.__defineGetter__(‘seconds‘, function() {return this.getSeconds();});  
Date.prototype.__defineSetter__(‘seconds‘, function(s) {this.setSeconds(s)});

Date.prototype.__defineGetter__("date", function (){return `${this.year}-${(this.month.dbl())}-${this.day.dbl()}`});
Date.prototype.__defineGetter__("time", function (){return `${this.hour.dbl()}:${this.minute.dbl()}:${this.seconds.dbl()}`});
Date.prototype.__defineGetter__("datetime", function (){return `${this.date} ${this.time}`});
  
// 将数字转换成2位的字符串，不足两位的在前面补0
Number.prototype.dbl = function (){
	return String(this).padStart(2, 0);
}

let num = 2;
log(num.dbl());

function doubleNum(n){
	return String(n).padStart(2, 0);
}

var now = new Date;  
log("%O",now); // 这样打印可以看到日期的属性和方法
let { year: y, month: m, day: d } = now;

log("年：%s",y) // 年：2019
log(y, m, d); // 2019 6 20
log(now.date); // 2019-06-20
log(now.time); // 10:56:53
log(now.datetime); // 2019-06-20 10:56:53