"yyyy-MM-dd HH:MM:SS"格式怎么正則獲取HH:MM這一部分

"yyyy-MM-dd HH:MM:SS"獲取HH:MM為什么要用正則啊，字符串截取不好么？

.substring()

timeString.match(/..:../)[0]

     var aaa = "2017-05-05 11:20:30";
    var bbb =  aaa.match(/\d+:\d+/)[0];
    console.log(bbb);
    //格式確定的話用split和substr也行console.log(aaa.split(" ")[1].substr(0,5));

([0-9]|0[0-9]|1[0-9]|2[0-3]):[0-5][0-9]

var str = "2017-12-19 16:34:25";
var reg = /^\d{4}-\d{2}-\d{2}\s(\d{2}:\d{2}):\d{2}$/;
console.log(str.match(reg)[1]);//16:34