How to Convert string time in 12-Hr format to integer then back

Question

I want to convert a 12-hour format time into a string, add some minutes, then convert back to string. My user will be entering a time as a sting example 8:03 AM this time needs to converted into an integer with 9 minutes added to it then converted back to the same 12-hour format just 9 minutes into the future.

I've tried to make a Date obj using the string time, but when I do the Date constructor says I am using an invalid date.

new Date("8:03 AM")

What I tried after that was adding a speicifc date to the time

new Date("09/10/2022 8:03 AM")

That worked to create a Date obj and then I would try to get just the time using .getTime() and pass that into my intToHHMM function.

const intToHHMM = function (time) {
    var sec_num = parseInt(time, 10); // don't forget the second param
    var hours   = Math.floor(sec_num / 3600);
    var minutes = Math.floor((sec_num - (hours * 3600)) / 60);
    var seconds = sec_num - (hours * 3600) - (minutes * 60);

    if (hours   < 10) {hours   = "0"+hours;}
    if (minutes < 10) {minutes = "0"+minutes;}
    if (seconds < 10) {seconds = "0"+seconds;}
    return hours+':'+minutes;
}

But I am getting a weird return that definitely is not hh:mm format.

Can someone lend a hand, I appreciate the help in advance!

Just edidted, Better? @EmielZuurbier – Carter James Sep 10 '22 at 20:30 — Carter James, Sep 10 '22 at 20:30

Omkar Pattanaik · Answer 1 · 2022-09-11T04:12:10.230

0

Just check this out. Modified for time input.

calc.addEventListener("click", function() {
  var time = document.getElementById("time").value
  var date=new Date();

  if(time){
   date = new Date(date.toLocaleDateString('en-US')+" "+time);
   }
  
  var options = {
    hour: 'numeric',
    minute: 'numeric',
    hour12: true
  };
  var timeString = date.toLocaleString('en-US', options);
  console.log(timeString);

  function addMinutes(date, minutes) {
      return new Date(date.getTime() + minutes*60000);
  }
  var timePlusNineMinString=addMinutes(date,9).toLocaleString('en-US', options);
  console.log(timePlusNineMinString);
})

Time:<input id="time" type="time" name="task_time" />
<button id="calc">Get Time</button>

edited Sep 11 '22 at 04:12

answered Sep 10 '22 at 20:34

Omkar Pattanaik

380
3
8

How can OP enter `"8:03 AM"` and get the requested date back? – Emiel Zuurbier Sep 10 '22 at 20:37
I just considered 2nd input in question i.e new Date("09/10/2022 8:03 AM") – Omkar Pattanaik Sep 10 '22 at 20:45
Ok this is great, but is there a way I can just enter the time and not the date? – Carter James Sep 10 '22 at 21:00

comrade254 · Answer 2 · 2022-09-10T21:32:00.253

check this function, pass any time and it will add minsToAdd minutes to start. Correct any mistakes when see them.

function addMins(start, minsToAdd) {
  let am_pm = start.split(" ")[1]
  let [hr, min] = start.split(" ")[0].split(":")
  let future = ""
  min = parseInt(min) + minsToAdd
  if (min > 59) {
    min = min - 60
    hr = parseInt(hr) + 1
    am_pm = hr > 11 ?
      am_pm === "PM" ? "AM" : "PM" :
      am_pm === "AM" ? "PM" : "AM";
    hr = hr > 12 ? hr - 12 : hr;
    future = [
      `${parseInt(hr)}`.length === 1 ? `0${hr}` : `${hr}`,
      `${min}`.length === 1 ? `0${min}` : `${min}`,
      am_pm
    ].join(":")
  } else {
    future = [`${hr}`.length === 1 ? `0${hr}` : `${hr}`,
      `${min}`.length === 1 ? `0${min}` : `${min}`,
      am_pm
    ].join(":")
  }
  return future

}

console.log(addMins("11:56 AM", 9)) //12:05:PM
console.log(addMins("11:56 PM", 9)) //12:05:AM
console.log(addMins("19:03 PM", 9)) //19:12:PM

score 0 · Answer 3 · answered Sep 11 '22 at 00:51

You don't need to involve Date methods here, just some magic:

const add9 = HM12 => {
  let [H, M, ampm] = HM12.split(/\W/);
  let minutes = (H % 12 + 12 * (ampm === 'PM')) * 60 - -M;
  
  minutes += 9; // magic
  
  M = (minutes % 60 + '').padStart(2, 0);
  H = minutes / 60 % 24|0;
  ampm = H < 12 ? 'AM' : 'PM';
  H = (H % 12 + '' || '12').padStart(2, 0);
  return `${H}:${M} ${ampm}`;
}

console.log('08:03 AM --> ' + add9('08:03 AM'))
console.log('11:53 PM --> ' + add9('11:53 PM'))
console.log('11:53 AM --> ' + add9('11:53 AM'))

How to Convert string time in 12-Hr format to integer then back

3 Answers3