Event Calendar Source Code in JavaScript

This JavaScript source code provides an Event Calendar that allows you to display and manage events. The calendar uses the Moment.js library to handle dates. It offers functionalities to navigate between months, view events, and categorize them with different colors.

The code initializes a calendar object and draws its header, month, and legend. Events can be added with specific details such as event name, calendar category, and color code. When you click on a day, it will show the events scheduled for that day.

The calendar simplifies event management, making it helpful for organizing and keeping track of various activities, whether for work, sports, kids’ events, or other purposes. This easy-to-use calendar is designed to improve your scheduling efficiency and help you stay organized.

How to Create an Event Calendar Using JavaScript

1. First of all, load the Moment JS by adding the following CDN link into the head tag of your webpage.

<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.5.1/moment.min.js"></script>

2. Create a div element with an id “calendar” and place it where you want to display the event calendar on your website.

<div id="calendar"></div>

3. Use the following CSS code to style the calendar widget. You can modify the CSS rules in order to customize it according to your needs.

*, *:before, *:after {
-moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box;
}

body {
 font-family: 'HelveticaNeue-UltraLight', 'Helvetica Neue UltraLight', 'Helvetica Neue', Arial, Helvetica, sans-serif;
 font-weight: 100;
 color: rgba(255, 255, 255, 1);
 margin: 0;
 padding: 0;
 background: #4A4A4A;
 -webkit-touch-callout: none;
 -webkit-user-select: none;
 -khtml-user-select: none;
 -moz-user-select: none;
 -ms-user-select: none;
 user-select: none;
}

#calendar {
  -webkit-transform: translate3d(0, 0, 0);
  -moz-transform: translate3d(0, 0, 0);
  transform: translate3d(0, 0, 0);
  width: 620px;
  margin: 0 auto;
  height: 570px;
  overflow: hidden;
}

.header {
  height: 50px;
  width: 620px;
  background: rgba(66, 66, 66, 1);
  text-align: center;
  position:relative;
  z-index: 100;
}

.header h1 {
  margin: 0;
  padding: 0;
  font-size: 20px;
  line-height: 50px;
  font-weight: 100;
  letter-spacing: 1px;
}

.left, .right {
  position: absolute;
  width: 0px;
  height: 0px;
  border-style: solid;
  top: 50%;
  margin-top: -7.5px;
  cursor: pointer;
}

.left {
  border-width: 7.5px 10px 7.5px 0;
  border-color: transparent rgba(160, 159, 160, 1) transparent transparent;
  left: 20px;
}

.right {
  border-width: 7.5px 0 7.5px 10px;
  border-color: transparent transparent transparent rgba(160, 159, 160, 1);
  right: 20px;
}

.month {
  /*overflow: hidden;*/
  opacity: 0;
}

.month.new {
  -webkit-animation: fadeIn 1s ease-out;
  opacity: 1;
}

.month.in.next {
  -webkit-animation: moveFromTopFadeMonth .4s ease-out;
  -moz-animation: moveFromTopFadeMonth .4s ease-out;
  animation: moveFromTopFadeMonth .4s ease-out;
  opacity: 1;
}

.month.out.next {
  -webkit-animation: moveToTopFadeMonth .4s ease-in;
  -moz-animation: moveToTopFadeMonth .4s ease-in;
  animation: moveToTopFadeMonth .4s ease-in;
  opacity: 1;
}

.month.in.prev {
  -webkit-animation: moveFromBottomFadeMonth .4s ease-out;
  -moz-animation: moveFromBottomFadeMonth .4s ease-out;
  animation: moveFromBottomFadeMonth .4s ease-out;
  opacity: 1;
}

.month.out.prev {
  -webkit-animation: moveToBottomFadeMonth .4s ease-in;
  -moz-animation: moveToBottomFadeMonth .4s ease-in;
  animation: moveToBottomFadeMonth .4s ease-in;
  opacity: 1;
}

.week {
 background: #4A4A4A;
}

.day {
  display: inline-block;
  width: 60px;
  padding: 10px;
  text-align: center;
  vertical-align: top;
  cursor: pointer;
  background: #4A4A4A;
  position: relative;
  z-index: 100;
}

.day.other {
 color: rgba(255, 255, 255, .3);
}

.day.today {
  color: rgba(156, 202, 235, 1);
}

.day-name {
  font-size: 9px;
  text-transform: uppercase;
  margin-bottom: 5px;
  color: rgba(255, 255, 255, .5);
  letter-spacing: .7px;
}

.day-number {
  font-size: 24px;
  letter-spacing: 1.5px;
}


.day .day-events {
  list-style: none;
  margin-top: 3px;
  text-align: center;
  height: 12px;
  line-height: 6px;
  overflow: hidden;
}

.day .day-events span {
  vertical-align: top;
  display: inline-block;
  padding: 0;
  margin: 0;
  width: 5px;
  height: 5px;
  line-height: 5px;
  margin: 0 1px;
}

.blue { background: rgba(156, 202, 235, 1); }
.orange { background: rgba(247, 167, 0, 1); }
.green { background: rgba(153, 198, 109, 1); }
.yellow { background: rgba(249, 233, 0, 1); }

.details {
  position: relative;
  width: 620px;
  height: 75px;
  background: rgba(164, 164, 164, 1);
  margin-top: 5px;
  border-radius: 4px;
}

.details.in {
  -webkit-animation: moveFromTopFade .5s ease both;
  -moz-animation: moveFromTopFade .5s ease both;
  animation: moveFromTopFade .5s ease both;
}

.details.out {
  -webkit-animation: moveToTopFade .5s ease both;
  -moz-animation: moveToTopFade .5s ease both;
  animation: moveToTopFade .5s ease both;
}

.arrow {
  position: absolute;
  top: -5px;
  left: 50%;
  margin-left: -2px;
  width: 0px;
  height: 0px;
  border-style: solid;
  border-width: 0 5px 5px 5px;
  border-color: transparent transparent rgba(164, 164, 164, 1) transparent;
  transition: all 0.7s ease;
}

.events {
  height: 75px;
  padding: 7px 0;
  overflow-y: auto;
  overflow-x: hidden;
}

.events.in {
  -webkit-animation: fadeIn .3s ease both;
  -moz-animation: fadeIn .3s ease both;
  animation: fadeIn .3s ease both;
}

.events.in {
  -webkit-animation-delay: .3s;
  -moz-animation-delay: .3s;
  animation-delay: .3s;
}

.details.out .events {
  -webkit-animation: fadeOutShrink .4s ease both;
  -moz-animation: fadeOutShink .4s ease both;
  animation: fadeOutShink .4s ease both;
}

.events.out {
  -webkit-animation: fadeOut .3s ease both;
  -moz-animation: fadeOut .3s ease both;
  animation: fadeOut .3s ease both;
}

.event {
  font-size: 16px;
  line-height: 22px;
  letter-spacing: .5px;
  padding: 2px 16px;
  vertical-align: top;
}

.event.empty {
  color: #eee;
}

.event-category {
  height: 10px;
  width: 10px;
  display: inline-block;
  margin: 6px 0 0;
  vertical-align: top;
}

.event span {
  display: inline-block;
  padding: 0 0 0 7px;
}

.legend {
  position: absolute;
  bottom: 0;
  width: 100%;
  height: 30px;
  background: rgba(60, 60, 60, 1);
  line-height: 30px;

}

.entry {
  position: relative;
  padding: 0 0 0 25px;
  font-size: 13px;
  display: inline-block;
  line-height: 30px;
  background: transparent;
}

.entry:after {
  position: absolute;
  content: '';
  height: 5px;
  width: 5px;
  top: 12px;
  left: 14px;
}

.entry.blue:after { background: rgba(156, 202, 235, 1); }
.entry.orange:after { background: rgba(247, 167, 0, 1); }
.entry.green:after { background: rgba(153, 198, 109, 1); }
.entry.yellow:after { background: rgba(249, 233, 0, 1); }

/* Animations are cool!  */
@-webkit-keyframes moveFromTopFade {
  from { opacity: .3; height:0px; margin-top:0px; -webkit-transform: translateY(-100%); }
}
@-moz-keyframes moveFromTopFade {
  from { height:0px; margin-top:0px; -moz-transform: translateY(-100%); }
}
@keyframes moveFromTopFade {
  from { height:0px; margin-top:0px; transform: translateY(-100%); }
}

@-webkit-keyframes moveToTopFade {
  to { opacity: .3; height:0px; margin-top:0px; opacity: 0.3; -webkit-transform: translateY(-100%); }
}
@-moz-keyframes moveToTopFade {
  to { height:0px; -moz-transform: translateY(-100%); }
}
@keyframes moveToTopFade {
  to { height:0px; transform: translateY(-100%); }
}

@-webkit-keyframes moveToTopFadeMonth {
  to { opacity: 0; -webkit-transform: translateY(-30%) scale(.95); }
}
@-moz-keyframes moveToTopFadeMonth {
  to { opacity: 0; -moz-transform: translateY(-30%); }
}
@keyframes moveToTopFadeMonth {
  to { opacity: 0; -moz-transform: translateY(-30%); }
}

@-webkit-keyframes moveFromTopFadeMonth {
  from { opacity: 0; -webkit-transform: translateY(30%) scale(.95); }
}
@-moz-keyframes moveFromTopFadeMonth {
  from { opacity: 0; -moz-transform: translateY(30%); }
}
@keyframes moveFromTopFadeMonth {
  from { opacity: 0; -moz-transform: translateY(30%); }
}

@-webkit-keyframes moveToBottomFadeMonth {
  to { opacity: 0; -webkit-transform: translateY(30%) scale(.95); }
}
@-moz-keyframes moveToBottomFadeMonth {
  to { opacity: 0; -webkit-transform: translateY(30%); }
}
@keyframes moveToBottomFadeMonth {
  to { opacity: 0; -webkit-transform: translateY(30%); }
}

@-webkit-keyframes moveFromBottomFadeMonth {
  from { opacity: 0; -webkit-transform: translateY(-30%) scale(.95); }
}
@-moz-keyframes moveFromBottomFadeMonth {
  from { opacity: 0; -webkit-transform: translateY(-30%); }
}
@keyframes moveFromBottomFadeMonth {
  from { opacity: 0; -webkit-transform: translateY(-30%); }
}

@-webkit-keyframes fadeIn  {
  from { opacity: 0; }
}
@-moz-keyframes fadeIn  {
  from { opacity: 0; }
}
@keyframes fadeIn  {
  from { opacity: 0; }
}

@-webkit-keyframes fadeOut  {
  to { opacity: 0; }
}
@-moz-keyframes fadeOut  {
  to { opacity: 0; }
}
@keyframes fadeOut  {
  to { opacity: 0; }
}

@-webkit-keyframes fadeOutShink  {
  to { opacity: 0; padding: 0px; height: 0px; }
}
@-moz-keyframes fadeOutShink  {
  to { opacity: 0; padding: 0px; height: 0px; }
}
@keyframes fadeOutShink  {
  to { opacity: 0; padding: 0px; height: 0px; }
}

4. Finally, add the following JavaScript function between the <script> tag or separate JS file to initialize the event calendar.

!function() {

  var today = moment();

  function Calendar(selector, events) {
    this.el = document.querySelector(selector);
    this.events = events;
    this.current = moment().date(1);
    this.draw();
    var current = document.querySelector('.today');
    if(current) {
      var self = this;
      window.setTimeout(function() {
        self.openDay(current);
      }, 500);
    }
  }

  Calendar.prototype.draw = function() {
    //Create Header
    this.drawHeader();

    //Draw Month
    this.drawMonth();

    this.drawLegend();
  }

  Calendar.prototype.drawHeader = function() {
    var self = this;
    if(!this.header) {
      //Create the header elements
      this.header = createElement('div', 'header');
      this.header.className = 'header';

      this.title = createElement('h1');

      var right = createElement('div', 'right');
      right.addEventListener('click', function() { self.nextMonth(); });

      var left = createElement('div', 'left');
      left.addEventListener('click', function() { self.prevMonth(); });

      //Append the Elements
      this.header.appendChild(this.title); 
      this.header.appendChild(right);
      this.header.appendChild(left);
      this.el.appendChild(this.header);
    }

    this.title.innerHTML = this.current.format('MMMM YYYY');
  }

  Calendar.prototype.drawMonth = function() {
    var self = this;
    
    this.events.forEach(function(ev) {
     ev.date = self.current.clone().date(Math.random() * (29 - 1) + 1);
    });
    
    
    if(this.month) {
      this.oldMonth = this.month;
      this.oldMonth.className = 'month out ' + (self.next ? 'next' : 'prev');
      this.oldMonth.addEventListener('webkitAnimationEnd', function() {
        self.oldMonth.parentNode.removeChild(self.oldMonth);
        self.month = createElement('div', 'month');
        self.backFill();
        self.currentMonth();
        self.fowardFill();
        self.el.appendChild(self.month);
        window.setTimeout(function() {
          self.month.className = 'month in ' + (self.next ? 'next' : 'prev');
        }, 16);
      });
    } else {
        this.month = createElement('div', 'month');
        this.el.appendChild(this.month);
        this.backFill();
        this.currentMonth();
        this.fowardFill();
        this.month.className = 'month new';
    }
  }

  Calendar.prototype.backFill = function() {
    var clone = this.current.clone();
    var dayOfWeek = clone.day();

    if(!dayOfWeek) { return; }

    clone.subtract('days', dayOfWeek+1);

    for(var i = dayOfWeek; i > 0 ; i--) {
      this.drawDay(clone.add('days', 1));
    }
  }

  Calendar.prototype.fowardFill = function() {
    var clone = this.current.clone().add('months', 1).subtract('days', 1);
    var dayOfWeek = clone.day();

    if(dayOfWeek === 6) { return; }

    for(var i = dayOfWeek; i < 6 ; i++) {
      this.drawDay(clone.add('days', 1));
    }
  }

  Calendar.prototype.currentMonth = function() {
    var clone = this.current.clone();

    while(clone.month() === this.current.month()) {
      this.drawDay(clone);
      clone.add('days', 1);
    }
  }

  Calendar.prototype.getWeek = function(day) {
    if(!this.week || day.day() === 0) {
      this.week = createElement('div', 'week');
      this.month.appendChild(this.week);
    }
  }

  Calendar.prototype.drawDay = function(day) {
    var self = this;
    this.getWeek(day);

    //Outer Day
    var outer = createElement('div', this.getDayClass(day));
    outer.addEventListener('click', function() {
      self.openDay(this);
    });

    //Day Name
    var name = createElement('div', 'day-name', day.format('ddd'));

    //Day Number
    var number = createElement('div', 'day-number', day.format('DD'));


    //Events
    var events = createElement('div', 'day-events');
    this.drawEvents(day, events);

    outer.appendChild(name);
    outer.appendChild(number);
    outer.appendChild(events);
    this.week.appendChild(outer);
  }

  Calendar.prototype.drawEvents = function(day, element) {
    if(day.month() === this.current.month()) {
      var todaysEvents = this.events.reduce(function(memo, ev) {
        if(ev.date.isSame(day, 'day')) {
          memo.push(ev);
        }
        return memo;
      }, []);

      todaysEvents.forEach(function(ev) {
        var evSpan = createElement('span', ev.color);
        element.appendChild(evSpan);
      });
    }
  }

  Calendar.prototype.getDayClass = function(day) {
    classes = ['day'];
    if(day.month() !== this.current.month()) {
      classes.push('other');
    } else if (today.isSame(day, 'day')) {
      classes.push('today');
    }
    return classes.join(' ');
  }

  Calendar.prototype.openDay = function(el) {
    var details, arrow;
    var dayNumber = +el.querySelectorAll('.day-number')[0].innerText || +el.querySelectorAll('.day-number')[0].textContent;
    var day = this.current.clone().date(dayNumber);

    var currentOpened = document.querySelector('.details');

    //Check to see if there is an open detais box on the current row
    if(currentOpened && currentOpened.parentNode === el.parentNode) {
      details = currentOpened;
      arrow = document.querySelector('.arrow');
    } else {
      //Close the open events on differnt week row
      //currentOpened && currentOpened.parentNode.removeChild(currentOpened);
      if(currentOpened) {
        currentOpened.addEventListener('webkitAnimationEnd', function() {
          currentOpened.parentNode.removeChild(currentOpened);
        });
        currentOpened.addEventListener('oanimationend', function() {
          currentOpened.parentNode.removeChild(currentOpened);
        });
        currentOpened.addEventListener('msAnimationEnd', function() {
          currentOpened.parentNode.removeChild(currentOpened);
        });
        currentOpened.addEventListener('animationend', function() {
          currentOpened.parentNode.removeChild(currentOpened);
        });
        currentOpened.className = 'details out';
      }

      //Create the Details Container
      details = createElement('div', 'details in');

      //Create the arrow
      var arrow = createElement('div', 'arrow');

      //Create the event wrapper

      details.appendChild(arrow);
      el.parentNode.appendChild(details);
    }

    var todaysEvents = this.events.reduce(function(memo, ev) {
      if(ev.date.isSame(day, 'day')) {
        memo.push(ev);
      }
      return memo;
    }, []);

    this.renderEvents(todaysEvents, details);

    arrow.style.left = el.offsetLeft - el.parentNode.offsetLeft + 27 + 'px';
  }

  Calendar.prototype.renderEvents = function(events, ele) {
    //Remove any events in the current details element
    var currentWrapper = ele.querySelector('.events');
    var wrapper = createElement('div', 'events in' + (currentWrapper ? ' new' : ''));

    events.forEach(function(ev) {
      var div = createElement('div', 'event');
      var square = createElement('div', 'event-category ' + ev.color);
      var span = createElement('span', '', ev.eventName);

      div.appendChild(square);
      div.appendChild(span);
      wrapper.appendChild(div);
    });

    if(!events.length) {
      var div = createElement('div', 'event empty');
      var span = createElement('span', '', 'No Events');

      div.appendChild(span);
      wrapper.appendChild(div);
    }

    if(currentWrapper) {
      currentWrapper.className = 'events out';
      currentWrapper.addEventListener('webkitAnimationEnd', function() {
        currentWrapper.parentNode.removeChild(currentWrapper);
        ele.appendChild(wrapper);
      });
      currentWrapper.addEventListener('oanimationend', function() {
        currentWrapper.parentNode.removeChild(currentWrapper);
        ele.appendChild(wrapper);
      });
      currentWrapper.addEventListener('msAnimationEnd', function() {
        currentWrapper.parentNode.removeChild(currentWrapper);
        ele.appendChild(wrapper);
      });
      currentWrapper.addEventListener('animationend', function() {
        currentWrapper.parentNode.removeChild(currentWrapper);
        ele.appendChild(wrapper);
      });
    } else {
      ele.appendChild(wrapper);
    }
  }

  Calendar.prototype.drawLegend = function() {
    var legend = createElement('div', 'legend');
    var calendars = this.events.map(function(e) {
      return e.calendar + '|' + e.color;
    }).reduce(function(memo, e) {
      if(memo.indexOf(e) === -1) {
        memo.push(e);
      }
      return memo;
    }, []).forEach(function(e) {
      var parts = e.split('|');
      var entry = createElement('span', 'entry ' +  parts[1], parts[0]);
      legend.appendChild(entry);
    });
    this.el.appendChild(legend);
  }

  Calendar.prototype.nextMonth = function() {
    this.current.add('months', 1);
    this.next = true;
    this.draw();
  }

  Calendar.prototype.prevMonth = function() {
    this.current.subtract('months', 1);
    this.next = false;
    this.draw();
  }

  window.Calendar = Calendar;

  function createElement(tagName, className, innerText) {
    var ele = document.createElement(tagName);
    if(className) {
      ele.className = className;
    }
    if(innerText) {
      ele.innderText = ele.textContent = innerText;
    }
    return ele;
  }
}();

!function() {
  var data = [
    { eventName: 'Lunch Meeting w/ Mark', calendar: 'Work', color: 'orange' },
    { eventName: 'Interview - Jr. Web Developer', calendar: 'Work', color: 'orange' },
    { eventName: 'Demo New App to the Board', calendar: 'Work', color: 'orange' },
    { eventName: 'Dinner w/ Marketing', calendar: 'Work', color: 'orange' },

    { eventName: 'Game vs Portalnd', calendar: 'Sports', color: 'blue' },
    { eventName: 'Game vs Houston', calendar: 'Sports', color: 'blue' },
    { eventName: 'Game vs Denver', calendar: 'Sports', color: 'blue' },
    { eventName: 'Game vs San Degio', calendar: 'Sports', color: 'blue' },

    { eventName: 'School Play', calendar: 'Kids', color: 'yellow' },
    { eventName: 'Parent/Teacher Conference', calendar: 'Kids', color: 'yellow' },
    { eventName: 'Pick up from Soccer Practice', calendar: 'Kids', color: 'yellow' },
    { eventName: 'Ice Cream Night', calendar: 'Kids', color: 'yellow' },

    { eventName: 'Free Tamale Night', calendar: 'Other', color: 'green' },
    { eventName: 'Bowling Team', calendar: 'Other', color: 'green' },
    { eventName: 'Teach Kids to Code', calendar: 'Other', color: 'green' },
    { eventName: 'Startup Weekend', calendar: 'Other', color: 'green' }
  ];

  

  function addDate(ev) {
    
  }

  var calendar = new Calendar('#calendar', data);

}();

That’s it! hopefully, you have successfully created an Event Calendar using this JavaScript source code. If you have any questions or suggestions, feel free to comment below.