How to Design a Simple Calendar using JavaScript ?

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In this article, we will see how to Create a calendar using HTML, CSS, and JavaScript that displays the current month and year, and allows the user to navigate to previous and next months. Also, it allows the user to jump to a specific month and year. The calendar should also highlight the current date.

Prerequisite: Basic knowledge of some front-end technologies like HTML, CSS, and JavaScript.

The task at hand is to create a webpage that displays a calendar. The calendar should have the functionality to navigate to the previous and next months. The calendar should also be able to display the current date in a different color.

Approach:

Create an HTML structure for the calendar using a table and appropriate list elements.
Create JavaScript variables to keep track of the current month and year, as well as elements to display the current month and year on the page.
Use JavaScript to create a function to display the current month’s calendar. This function should take in the current month and year as arguments and use them to determine the number of days in the current month, and the first day of the month, and fill in the appropriate number of days in the calendar.
Create JavaScript functions to navigate to the next and previous months.
Use JavaScript to add event listeners to the appropriate elements (next and previous buttons) to call the appropriate navigation functions when clicked.

Implementation: Below is the implementation of the above approach:

index.html: This file contains the skeleton of calendar
style.css: This file contains CSS to improve the look of the calendar
script.js: This file contains the code to make the calendar dynamic

Example: Here is the implementation of the above-explained steps.

HTML

<!DOCTYPE html>
<html lang="en" dir="ltr">
 
<head>
    <meta charset="utf-8">
    <title>Calendar</title>
    <meta name="viewport"
          content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet"
        href=
"https://fonts.googleapis.com/css2?family=Material+Symbols+Rounded:opsz,wght,FILL,GRAD@20..48,100..700,0..1,-50..200">
</head>
 
<body>
    <div class="calendar-container">
        <header class="calendar-header">
            <p class="calendar-current-date"></p>
            <div class="calendar-navigation">
                <span id="calendar-prev"
                      class="material-symbols-rounded">
                    chevron_left
                </span>
                <span id="calendar-next"
                      class="material-symbols-rounded">
                    chevron_right
                </span>
            </div>
        </header>
 
        <div class="calendar-body">
            <ul class="calendar-weekdays">
                <li>Sun</li>
                <li>Mon</li>
                <li>Tue</li>
                <li>Wed</li>
                <li>Thu</li>
                <li>Fri</li>
                <li>Sat</li>
            </ul>
            <ul class="calendar-dates"></ul>
        </div>
    </div>
</body>
</html>

CSS

* {
    margin: 0;
    padding: 0;
    font-family: 'Poppins', sans-serif;
}
 
body {
    display: flex;
    background: #ef62da;
    min-height: 100vh;
    padding: 0 10px;
    align-items: center;
    justify-content: center;
}
 
.calendar-container {
    background: #fff;
    width: 450px;
    border-radius: 10px;
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.12);
}
 
.calendar-container header {
    display: flex;
    align-items: center;
    padding: 25px 30px 10px;
    justify-content: space-between;
}
 
header .calendar-navigation {
    display: flex;
}
 
header .calendar-navigation span {
    height: 38px;
    width: 38px;
    margin: 0 1px;
    cursor: pointer;
    text-align: center;
    line-height: 38px;
    border-radius: 50%;
    user-select: none;
    color: #aeabab;
    font-size: 1.9rem;
}
 
.calendar-navigation span:last-child {
    margin-right: -10px;
}
 
header .calendar-navigation span:hover {
    background: #f2f2f2;
}
 
header .calendar-current-date {
    font-weight: 500;
    font-size: 1.45rem;
}
 
.calendar-body {
    padding: 20px;
}
 
.calendar-body ul {
    list-style: none;
    flex-wrap: wrap;
    display: flex;
    text-align: center;
}
 
.calendar-body .calendar-dates {
    margin-bottom: 20px;
}
 
.calendar-body li {
    width: calc(100% / 7);
    font-size: 1.07rem;
    color: #414141;
}
 
.calendar-body .calendar-weekdays li {
    cursor: default;
    font-weight: 500;
}
 
.calendar-body .calendar-dates li {
    margin-top: 30px;
    position: relative;
    z-index: 1;
    cursor: pointer;
}
 
.calendar-dates li.inactive {
    color: #aaa;
}
 
.calendar-dates li.active {
    color: #fff;
}
 
.calendar-dates li::before {
    position: absolute;
    content: "";
    z-index: -1;
    top: 50%;
    left: 50%;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    transform: translate(-50%, -50%);
}
 
.calendar-dates li.active::before {
    background: #6332c5;
}
 
.calendar-dates li:not(.active):hover::before {
    background: #e4e1e1;
}

Javascript

let date = new Date();
let year = date.getFullYear();
let month = date.getMonth();
 
const day = document.querySelector(".calendar-dates");
 
const currdate = document
    .querySelector(".calendar-current-date");
 
const prenexIcons = document
    .querySelectorAll(".calendar-navigation span");
 
// Array of month names
const months = [
    "January",
    "February",
    "March",
    "April",
    "May",
    "June",
    "July",
    "August",
    "September",
    "October",
    "November",
    "December"
];
 
// Function to generate the calendar
const manipulate = () => {
 
    // Get the first day of the month
    let dayone = new Date(year, month, 1).getDay();
 
    // Get the last date of the month
    let lastdate = new Date(year, month + 1, 0).getDate();
 
    // Get the day of the last date of the month
    let dayend = new Date(year, month, lastdate).getDay();
 
    // Get the last date of the previous month
    let monthlastdate = new Date(year, month, 0).getDate();
 
    // Variable to store the generated calendar HTML
    let lit = "";
 
    // Loop to add the last dates of the previous month
    for (let i = dayone; i > 0; i--) {
        lit +=
            `<li class="inactive">${monthlastdate - i + 1}</li>`;
    }
 
    // Loop to add the dates of the current month
    for (let i = 1; i <= lastdate; i++) {
 
        // Check if the current date is today
        let isToday = i === date.getDate()
            && month === new Date().getMonth()
            && year === new Date().getFullYear()
            ? "active"
            : "";
        lit += `<li class="${isToday}">${i}</li>`;
    }
 
    // Loop to add the first dates of the next month
    for (let i = dayend; i < 6; i++) {
        lit += `<li class="inactive">${i - dayend + 1}</li>`
    }
 
    // Update the text of the current date element 
    // with the formatted current month and year
    currdate.innerText = `${months[month]} ${year}`;
 
    // update the HTML of the dates element 
    // with the generated calendar
    day.innerHTML = lit;
}
 
manipulate();
 
// Attach a click event listener to each icon
prenexIcons.forEach(icon => {
 
    // When an icon is clicked
    icon.addEventListener("click", () => {
 
        // Check if the icon is "calendar-prev"
        // or "calendar-next"
        month = icon.id === "calendar-prev" ? month - 1 : month + 1;
 
        // Check if the month is out of range
        if (month < 0 || month > 11) {
 
            // Set the date to the first day of the 
            // month with the new year
            date = new Date(year, month, new Date().getDate());
 
            // Set the year to the new year
            year = date.getFullYear();
 
            // Set the month to the new month
            month = date.getMonth();
        }
 
        else {
 
            // Set the date to the current date
            date = new Date();
        }
 
        // Call the manipulate function to 
        // update the calendar display
        manipulate();
    });
});