如何在JavaScript中將“ 12:00 PM”轉換為Date對象？

Question

var time = "12:00 PM"
var startTime = Date.parse(time); // output is NaN
alert(startTime);

如何在JavaScript中將字符串時間轉換為時間對象？

所需的輸出= 2014年8月14日，星期四，格林尼治標准時間+0530（IST）

因為我需要將startTime與當前時間進行比較...

Answer 1

參見Date.prototype.setHours()

var d = new Date();
d.setHours(12, 0, 0, 0);
alert(d);

如果必須解析時間字符串，則可以嘗試此操作...

var time = '12:00 PM';
var startTime = new Date();
var parts = time.match(/(\d+):(\d+) (AM|PM)/);
if (parts) {
    var hours = parseInt(parts[1]),
        minutes = parseInt(parts[2]),
        tt = parts[3];
    if (tt === 'PM' && hours < 12) hours += 12;
    startTime.setHours(hours, minutes, 0, 0);
}
alert(startTime);

JSFiddle〜http: //jsfiddle.net/tp1L63bu/

Answer 2

清理/合並/測試邊際案例，Phil以上建議：

const militaryTime = (time, date = new Date()) => {
  const parts = time.trim().match(/(\d+):(\d+)\s?((am|AM)|(pm|PM))/)
  const p = {
    hours: parseInt(parts[1]),
    minutes: parseInt(parts[2]),
    period: parts[3].toLowerCase()
  }

  if (p.hours === 12) {
    if (p.period === 'am') {
      date.setHours(p.hours - 12, p.minutes)
    }
    if (p.period === 'pm') {
      date.setHours(p.hours, p.minutes)
    }
  } else {
    if (p.period === 'am') {
      date.setHours(p.hours, p.minutes)
    }
    if (p.period === 'pm') {
      date.setHours(p.hours + 12, p.minutes)
    }
  }

  return date
}

militaryTime('  4:00 am    ') // Thu May 30 2019 04:00:48 GMT-0400 (Eastern Daylight Time)
militaryTime('4:00pm') // Thu May 30 2019 16:00:42 GMT-0400 (Eastern Daylight Time)

militaryTime('12:00am') // Thu May 30 2019 00:00:25 GMT-0400 (Eastern Daylight Time)
militaryTime('12:00pm') // Thu May 30 2019 12:00:46 GMT-0400 (Eastern Daylight Time)