Best way to convert military time to standard time in javascript

Question

What is the best way to convert military time to am and pm time. . I have the following code and it works fine:

$scope.convertTimeAMPM = function(time){
//var time = "12:23:39";
var time = time.split(':');
var hours = time[0];
var minutes = time[1];
var seconds = time[2];
$scope.timeValue = "" + ((hours >12) ? hours -12 :hours);
    $scope.timeValue += (minutes < 10) ? ":0" : ":" + minutes;
    $scope.timeValue += (seconds < 10) ? ":0" : ":" + seconds;
    $scope.timeValue += (hours >= 12) ? " P.M." : " A.M.";
    //console.log( timeValue);
}

But I am not satisfied in the output shows when I run my program. .

Sample output:

20:00:00   8:0:0 P.M.
08:00:00   08:0:0 A.M
16:00:00   4:30:0 P.M.

I want to achieve the output which looks like the following:

20:00:00   8:00:00 P.M.
08:00:00   8:00:00 A.M
16:30:00   4:30:00 P.M.

Is there any suggestions there? Thanks

Answer 1

You missed concatenating the string when minutes < 10 and seconds < 10 so you were not getting the desired result.

Convert string to number using Number() and use it appropriately as shown in the working code snippet below:

EDIT: Updated code to use Number() while declaration of hours, minutes and seconds.

var time = "16:30:00"; // your input

time = time.split(':'); // convert to array

// fetch
var hours = Number(time[0]);
var minutes = Number(time[1]);
var seconds = Number(time[2]);

// calculate
var timeValue;

if (hours > 0 && hours <= 12) {
  timeValue= "" + hours;
} else if (hours > 12) {
  timeValue= "" + (hours - 12);
} else if (hours == 0) {
  timeValue= "12";
}
 
timeValue += (minutes < 10) ? ":0" + minutes : ":" + minutes;  // get minutes
timeValue += (seconds < 10) ? ":0" + seconds : ":" + seconds;  // get seconds
timeValue += (hours >= 12) ? " P.M." : " A.M.";  // get AM/PM

// show
alert(timeValue);
console.log(timeValue);

Read up: Number() | MDN

Answer 2

As Nit recommend, Moment.js provides a simple solution to your problem.

function convert(input) {
    return moment(input, 'HH:mm:ss').format('h:mm:ss A');
}

console.log(convert('20:00:00'));
console.log(convert('08:00:00'));
console.log(convert('16:30:00'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.9.0/moment.js"></script>

Answer 3

As an extension to Huy Hoang Pham's answer, here's the code with Luxon rather than moment.js (see this and this)

import { DateTime }  from "luxon";

function convert(input) {
    return DateTime.fromFormat(input, 'HH:mm:ss').toFormat('h:mm:ss A');
}

console.log(convert('20:00:00'));
console.log(convert('08:00:00'));
console.log(convert('16:30:00'));

Time is complicated, and I would recommend using a library over your own code for conversions like this.

Answer 4

A compact way to do it using ES6 can be the following:

toRegularTime = (militaryTime) => {
    const [hours, minutes, seconds] = militaryTime.split(':');
    return `${(hours > 12) ? hours - 12 : hours}:${minutes}${seconds ? `:${seconds}` : ''} ${(hours >= 12) ? 'PM' : 'AM'}`;
}

Answer 5

const parseMillitaryTime = (time: string) =>
    pipe(
      time,
      s => s.split(':'),
      time_ =>
        `${((Number(time_[0]) + 11) % 12) + 1}:${
          Number(time_[1]) < 10 ? `0${Number(time_[1])}` : `${Number(time_[1])}`
        } ${Number(time_[0]) > 11 ? 'pm' : 'am'}`
    )

Answer 6

The function toLocaleTimeString() did it for me.

From the documentation: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleTimeString

 // Depending on timezone, your results will vary
 const event = new Date('August 19, 1975 23:15:30 GMT+00:00');

 console.log(event.toLocaleTimeString('en-US'));
 // expected output: 1:15:30 AM

Answer 7

How about this as a helper function?

let convertMilitaryToStandard = function(time) {
  let timeParts = time.split(":");
  let standardTime = "";

  if (parseInt(timeParts[0]) > 12) {
    timeParts[0] = timeParts[0] - 12;
    standardTime = timeParts.join(":") + " PM";
  } else if (parseInt(timeParts[0]) === 12) {
    standardTime = timeParts.join(":") + " PM";
  } else {
    standardTime = timeParts.join(":") + " AM";
  }

  return standardTime;
}

console.log(convertMilitaryToStandard("12:15:12"));
console.log(convertMilitaryToStandard("01:15:12"));
console.log(convertMilitaryToStandard("18:15"));

Answer 8

No need for a library ?

Here's a sweet & simple function I whipped up that should suit your needs exactly

function toStandardTime(militaryTime) {
    militaryTime = militaryTime.split(':');
    return (militaryTime[0].charAt(0) == 1 && militaryTime[0].charAt(1) > 2) ? (militaryTime[0] - 12) + ':' + militaryTime[1] + ':' + militaryTime[2] + ' P.M.' : militaryTime.join(':') + ' A.M.'
}

console.log(toStandardTime('16:30:00'));

And a more readable version in case it's needed

function toStandardTime(militaryTime) {
  militaryTime = militaryTime.split(':');
  if (militaryTime[0].charAt(0) == 1 && militaryTime[0].charAt(1) > 2) {
    return (militaryTime[0] - 12) + ':' + militaryTime[1] + ':' + militaryTime[2] + ' P.M.';
  } else {
    return militaryTime.join(':') + ' A.M.';
  }
}

console.log(toStandardTime('16:30:00'));