Time conversion

Prepare your favorite cup of coffee because we are about to enter the fantastic world of Time conversion.

What is a time conversion?

A time is represented in the format 12 hours, of hh:mm:ssAM/PM. We must convert to 24-hour format. If the time is 12:00:00AM, it will be represented as 00:00:00. If the time is 12:00:00PM, it will be represented as 12:00:00.

Let's learn how to convert a time from hh:mm:ssAM/PM to hh:mm:ss.

If we have the time 07:05:45PM, we should return 19:05:45

const s = '07:05:45PM';

The first step is to divide the time into parts, for this we will use the slice method which will limit the time string to 8 positions, so as not to consider the suffix AM or PM.

s.slice(0,8) // '07:05:45'

Now we must obtain the hour, minute and second, for this we will use the split method and pass the : parameter so that the positions of the hours, minutes and seconds are separated.

s.slice(0,8).split(':') // ['07', '05', '45']

Since we already have the hour, minute and second, we will assign constants to collect each value

const [hour, minute, second] = s.slice(0,8).split(':');
// hour = '07'
// minute = '05'
// second = '45'

In this problem, it will only be necessary to modify the hour value to convert AM/PM to 24-hour format. So let's check if the time string has PM in its structure

s.includes('PM') // true

The includes method will return true if the value is contained in the string and false if the value is not contained in the string

If the hour string has the PM we will convert the format from 12 hours to 24 hours as follows:

hour == 12 ? '12' : Number(hour) + 12

If the time is 12PM, it will continue with the number 12. For other cases we will add 12 units to the hour.

When the time is AM, we will have the following validation:

hour == 12 ? '00' : hour

For 12AM we will consider the value 00. For other values the time will remain the same.

Finally, we simply return a string concatenating the converted hour, minute and second

return `${hour}:${minute}:${second}`

Our final resolution to the problem is:

const s = '07:05:45PM';

const [hour, minute, second] = s.slice(0,8).split(':');

hour = s.includes('PM') ?
    (hour == 12 ? '12' : Number(hour) + 12) :
    (hour == 12 ? '00' : hour);

return `${hour}:${minute}:${second}`;

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