JavaScript Program to Convert String to 24-hour Time Format

In this article, we are going to learn about the conversion of a string to a 24-hour time format in JavaScript, converting a string to a 24-hour time format involves transforming a time representation from the traditional 12-hour clock (AM/PM) to the 24-hour clock (00:00 to 23:59).

There are several methods that can be used to convert a string to a 24-hour time format in JavaScript, which are listed below:

We will explore all the above methods along with their basic implementation with the help of examples.

Approach 1: Using String Manipulation

This approach involves splitting the input string using the delimiter, extracting the hour and minute components, and converting them to a 24-hour format.

Syntax:

const [time, period] = timeString.split(' ');
const [hour, minute] = time.split(':');
let formattedHour = parseInt(hour);

Example: In this example, we are using the above approach.

Javascript

function convertTo24HourFormat(timeString) {
    const [time, period] = timeString.split(' ');
    const [hour, minute] = time.split(':');
    let formattedHour = parseInt(hour);

    if (period === 'PM') {
        formattedHour += 12;
    }

    return `${formattedHour}:${minute}`;
}

const inputTime = '03:30 PM';
const formattedTime = convertTo24HourFormat(inputTime);
console.log(formattedTime);

Output

15:30

Approach 2: Using Regular Expressions

Regular expressions can help extract the hour, minute, and AM/PM components from the input string. The AM/PM component is then used to adjust the hour value.

Syntax:

const match = timeString.match(/(\d+):(\d+) (\w+)/);

Example: In this example Regular expressions split time into hour, minute, and period. Adjust hour based on period to 24-hour format. Combine components into a formatted string.

Javascript

function convertTo24HourFormat(timeString) {
    const match = timeString.match(/(\d+):(\d+) (\w+)/);
    const hour = parseInt(match[1]);
    const minute = match[2];
    const period = match[3];
    let formattedHour = hour;

    if (period === 'PM' && hour < 12) {
        formattedHour += 12;
    }

    return `${formattedHour}:${minute}`;
}

const inputTime = '4:45 PM';
const formattedTime = convertTo24HourFormat(inputTime);
console.log(formattedTime);

Output

16:45

Approach 3: Using the Date Object

In this approach, using the Date object, input time is set with a common date. The formatted time is extracted in 24-hour format using toLocaleTimeString.

Syntax:

let formattedTime = date.toLocaleTimeString('en-US', { hour12: false });

Example: In this approach we are using the above-explained approach.

Javascript

function convertTo24Hour(timeString) {
    let date = new Date(`01/01/2022 ${timeString}`);
    let formattedTime = date.toLocaleTimeString('en-US',
        { hour12: false });
    return formattedTime;
}

let inputTime = '09:15 PM';
let formattedTime = convertTo24Hour(inputTime);
console.log(formattedTime);

Output

21:15:00