（一）時間戳轉為當前時間

	var a = 1594810549
	
	console.log(timestampToTime(a)) //2020-07-15->18:55:49

	function timestampToTime(timestamp){
		var date = new Date(timestamp * 1000);//時間戳為10位需*1000，時間戳為13位的話不需乘1000
		Y = date.getFullYear() + '-';
		M = (date.getMonth()+1 < 10 ? '0'+(date.getMonth()+1) : date.getMonth()+1) + '-';
		D = date.getDate() < 10 ? '0'+(date.getDate()) : date.getDate();
		h = date.getHours() + ':';
		m = date.getMinutes() + ':';
		s = date.getSeconds();
		return Y+M+D+ '->' +h+m+s;
	}

（二）當前時間轉為時間戳

	var date = new Date('2020-7-15 18:55:49:123');//後三位為毫秒
	    var time1 = date.getTime();
	    var time2 = date.valueOf();
	    var time3 = Date.parse(date);
	    console.log(time1);//1594810549123
	    console.log(time2);//1594810549123
	    console.log(time3);//1594810549000
		

　附帶一個for in 小迴圈

	var b = [1,2,3,4]
	for(let index in b){
		console.log(b[index])
	}