Simple Date Picker in Pure Javascript CSS (Free Download)

There sure are a lot of date pickers on the Internet for jQuery, Bootstrap, React, and whatever else. But I understand, it really does not make any sense to load an entire library, just for the sake of a simple plugin. So here it is, a sharing of my simple lightweight date picker, all done in pure CSS Javascript – Read on!

ⓘ I have included a zip file with all the source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

 

TABLE OF CONTENTS

Download & Demo	How It Works	Useful Bits
The End

 

 

 

QUICK NOTES

If you spot a bug, feel free to comment below. I try to answer short questions too, but it is one person versus the entire world… If you need answers urgently, please check out my list of websites to get help with programming.

 

SOURCE CODE DOWNLOAD

Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

EXAMPLE 1) POPUP DATE PICKER

<!-- (A) LOAD DATE PICKER -->
<link href="dp-light.css" rel="stylesheet">
<script defer src="datepicker.js"></script>
 
<!-- (B) THE HTML -->
<input type="text" id="input-pop" placeholder="Popup"/>
 
<!-- (C) ATTACH DATE PICKER ON LOAD -->
<script>
window.addEventListener("load", () => {
  picker.attach({ target: "input-pop" });
});
</script>

This is the simplest way to use the date picker.

1. Load the date picker CSS and Javascript. Doh.
2. Define the HTML <input> field, give it an id.
3. Use picker.attach() to attach the date picker – Just specify the target HTML field (id of the HTML field).

 

 

EXAMPLE 2) INLINE DATE PICKER

<!-- (B) THE HTML -->
<input type="text" id="input-inline" placeholder="Inline"/>
<div id="pick-inline"></div>
 
<!-- (C) ATTACH DATE PICKER ON LOAD -->
<script>
window.addEventListener("load", () => {
  picker.attach({
    target: "input-inline",
    container: "pick-inline"
  });
});
</script>

Pretty much the same, but we now also define a <div> to spawn the date picker inline.

 

EXAMPLE 3) ALL DATE PICKER OPTIONS

<!-- (B) THE HTML -->
input type="text" id="input-opt" placeholder="Options"/>
<div id="pick-opt"></div>
 
<!-- (C) ATTACH DATE PICKER ON LOAD -->
<script>
window.addEventListener("load", () => {
  picker.attach({
    target: "input-opt",
    container: "pick-opt",
    disableday : [2, 7], 
    startmon: true, 
    yrange: 5, 
    onpick: () => { alert("PICKED"); } 
  });
});
</script>

The date picker also takes in a couple of options:

• disableday An array to disable certain days. For example, [2, 7] will disable Tuesdays and Sundays.
• startmon To set if the week starts on a Monday. By default, this is false and the week starts on Sunday.
• yrange The selectable year range. This defaults to +/- 10 years.
• onpick Function to run upon picking a date.

 

 

 

PART A) ATTACH DATE PICKER

// (A) ATTACH DATEPICKER TO TARGET
// target: field to populate
// container: generate datepicker in here (for inline datepicker)
// startmon: start on mon? (optional, default false)
// yrange: year select range (optional, default 10)
// disableday: days to disable, e.g. [2,7] to disable tue and sun (optional)
// onpick : function to call on select date (optional)
instances : [],
attach : (opt) => {
  // (A1) SET DEFAULT OPTIONS & REGISTER INSTANCE
  opt.target = document.getElementById(opt.target);
  opt.target.readOnly = true; // PREVENT ONSCREEN KEYBOARD
  if (opt.container) { opt.container = document.getElementById(opt.container); }
  opt.startmon = opt.startmon ? true : false;
  opt.yrange = opt.yrange ? opt.yrange : 10;
  const id = picker.instances.length;
  picker.instances.push(opt);
  let inst = picker.instances[id];
 
  // (A2) TEMP VARS + CURRENT MONTH YEAR (UTC+0)
  let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
                "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
  temp, today = new Date(),
  thisMonth = today.getUTCMonth(), // JAN IS 0
  thisYear = today.getUTCFullYear();
 
  // (A3) GENERATE HTML
  // (A3-1) HTML DATEPICKER WRAPPER
  inst.hPick = document.createElement("div");
  inst.hPick.classList.add("picker");
 
  // (A3-2) HTML MONTH SELECT
  inst.hMonth = document.createElement("select");
  inst.hMonth.classList.add("picker-m");
  for (let m in months) {
    temp = document.createElement("option");
    temp.value = +m + 1;
    temp.text = months[m];
    inst.hMonth.appendChild(temp);
  }
  inst.hMonth.selectedIndex = thisMonth;
  inst.hMonth.onchange = () => { picker.draw(id); };
  inst.hPick.appendChild(inst.hMonth);
 
  // (A3-3) HTML YEAR SELECT
  inst.hYear = document.createElement("select");
  inst.hYear.classList.add("picker-y");
  for (let y = thisYear-inst.yrange; y < thisYear+inst.yrange; y++) {
    temp = document.createElement("option");
    temp.value = y;
    temp.text = y;
    inst.hYear.appendChild(temp);
  }
  inst.hYear.selectedIndex = inst.yrange;
  inst.hYear.onchange = () => { picker.draw(id); };
  inst.hPick.appendChild(inst.hYear);
 
  // (A3-4) HTML DAYS
  inst.hDays = document.createElement("div");
  inst.hDays.classList.add("picker-d");
  inst.hPick.appendChild(inst.hDays);
  picker.draw(id);
 
  // (A4) INLINE DATEPICKER - ATTACH INTO CONTAINER
  if (inst.container) { inst.container.appendChild(inst.hPick); }
 
  // (A5) POPUP DATEPICKER - ATTACH INTO HTML BODY
  else {
    // (A5-1) FULL PAGE WRAPPER
    inst.hWrap = document.createElement("div");
    inst.hWrap.classList.add("picker-wrap");
    inst.hWrap.appendChild(inst.hPick);
 
    // (A5-2) CLICK TO TOGGLE DATEPICKER
    inst.target.onfocus = () => {
      inst.hWrap.classList.add("show");
    };
    inst.hWrap.onclick = (evt) => { if (evt.target == inst.hWrap) {
      inst.hWrap.classList.remove("show");
    }};
 
    // (A5-3) ATTACH POPUP DATEPICKER
    document.body.appendChild(inst.hWrap);
  }
}

You have already seen this one – picker.attach() is used to attach the date picker to your specified container. It’s long-winded but straightforward:

• Register the date picker and options into picker.instances. Yes, this is to distinguish which is which if multiple date pickers are created on the same page.
• Generate the HTML of the date picker – We will go through that below.

 

 

PART B) DRAW DAYS IN MONTH

// (B) DRAW DAYS IN MONTH
draw : (id) => {
  // (B1) CRAZY VARS & CALCULATIONS
  // (B1-1) GET INSTANCE + SELECTED MONTH YEAR
  let inst = picker.instances[id],
      month = inst.hMonth.value,
      year = inst.hYear.value;
 
  // (B1-2) DATE RANGE CALCULATION (UTC+0)
  let daysInMonth = new Date(Date.UTC(year, month, 0)).getUTCDate(),
      startDay = new Date(Date.UTC(year, month-1, 1)).getUTCDay(), // SUN IS 0
      endDay = new Date(Date.UTC(year, month-1, daysInMonth)).getUTCDay();
      startDay = startDay==0 ? 7 : startDay,
      endDay = endDay==0 ? 7 : endDay;
 
  // (B1-3) TODAY (FOR HIGHLIGHTING "TODAY'S DATE CELL")
  let today = new Date(), todayDate = null;
  if (today.getUTCMonth()+1 == month && today.getUTCFullYear() == year) {
    todayDate = today.getUTCDate();
  }
 
  // (B1-4) DAY NAMES
  let daynames = ["Mon", "Tue", "Wed", "Thur", "Fri", "Sat"];
  if (inst.startmon) { daynames.push("Sun"); }
  else { daynames.unshift("Sun"); }
 
  // (B1-5) FOR GENERATING DATE SQUARES
  let table, row, cell, squares = [];
 
  // (B2) CALCULATE DATE SQUARES ARRAY
  // (B2-1) EMPTY SQUARES BEFORE FIRST DAY OF MONTH
  if (inst.startmon && startDay!=1) {
    for (let i=1; i<startDay; i++) { squares.push("B"); }
  }
  if (!inst.startmon && startDay!=7) {
    for (let i=0; i<startDay; i++) { squares.push("B"); }
  }
 
  // (B2-2) DAYS OF MONTH (SOME DAYS DISABLED)
  if (inst.disableday) {
    let thisDay = startDay;
    for (let i=1; i<=daysInMonth; i++) {
      squares.push([i, inst.disableday.includes(thisDay)]);
      thisDay++;
      if (thisDay==8) { thisDay = 1; }
    }
  }
 
  // (B2-3) DAYS OF MONTH (ALL DAYS ENABLED)
  else {
    for (let i=1; i<=daysInMonth; i++) { squares.push([i, false]); }
  }
 
  // (B2-4) EMPTY SQUARES AFTER LAST DAY OF MONTH
  if (inst.startmon && endDay!=7) {
    for (let i=endDay; i<7; i++) { squares.push("B"); }
  }
  if (!inst.startmon && endDay!=6) {
    for (let i=endDay; i<(endDay==7?13:6); i++) { squares.push("B"); }
  }
 
  // (B3) DRAW HTML
  // (B3-1) HTML DAY NAMES HEADER
  table = document.createElement("table");
  row = table.insertRow();
  row.classList.add("picker-d-h");
  for (let d of daynames) {
    cell = row.insertCell();
    cell.innerHTML = d;
  }
 
  // (B3-2) HTML DATE CELLS
  row = table.insertRow();
  for (let i=0; i<squares.length; i++) {
    if (i!=squares.length && i%7==0) { row = table.insertRow(); }
    cell = row.insertCell();
    if (squares[i] == "B") { cell.classList.add("picker-d-b"); }
    else {
      // CELL DATE
      cell.innerHTML = squares[i][0];
 
      // NOT ALLOWED TO CHOOSE THIS DAY
      if (squares[i][1]) { cell.classList.add("picker-d-dd"); }
 
      // ALLOWED TO CHOOSE THIS DAY
      else {
        if (squares[i][0] == todayDate) { cell.classList.add("picker-d-td"); }
        cell.classList.add("picker-d-d");
        cell.onclick = () => { picker.pick(id, squares[i][0]); }
      }
    }
  }
 
  // (B4) ATTACH DAYS TO DATEPICKER
  inst.hDays.innerHTML = "";
  inst.hDays.appendChild(table);
}

This function deals with the generation of the HTML days in months. It is fired from picker.attach(), and whenever the month/year is changed. Some crazy calculations are involved here:

• (B1) Get the selected month/year. Calculate the days in the month, the start date, end date, etc…
• (B2) Take note, we do not generate the HTML immediately. We calculate the days and keep them in the array squares.
  • Basically, every month is not guaranteed to start on a Sunday (or Monday). So there may be a number of “blank squares” before the first day of the month – This is padded by pushing B into squares.
  • Then the individual days will be populated into squares, these are arrays with 2 elements. The first element is the day of the month, the second is a boolean to indicate if this day is disabled.
  • Every month is also not guaranteed to end on a Saturday (or Sunday). So if necessary, we do the same and pad squareswith B after the last day of the month.
• (B3 & B4) The actual HTML generation.

 

 

PART C) PICK A DATE

// (C) CHOOSE A DATE
pick : (id, day) => {
  // (C1) GET MONTH YEAR
  let inst = picker.instances[id],
      month = inst.hMonth.value,
      year = inst.hYear.value;
 
  // (C2) FORMAT & SET SELECTED DAY (YYYY-MM-DD)
  if (+month<10) { month = "0" + month; }
  if (+day<10) { day = "0" + day; }
  inst.target.value = `${year}-${month}-${day}`;
 
  // (C3) POPUP ONLY - CLOSE
  if (inst.container === undefined) {
    inst.hWrap.classList.remove("show");
  }
 
  // (C4) CALL ON PICK IF DEFINED
  if (inst.onpick) { inst.onpick(); }
}

As you can guess, this function simply gets the selected date and returns a nicely formatted string. I have set it to use the ISO 8601 date format of YYYY-MM-DD, but feel free to change it as you see fit.

 

EXTRA) DATE PICKER HTML & CSS

This is the HTML that the Javascript generates… A little messy, but feel free to change the CSS theme to your own liking.

 

 

DISABLING CERTAIN DAYS

Everyone has a different requirement –

• Disable specific days.
• Disable past days.
• Allow only past days (disable future days).
• Only enable from tomorrow to N days later.
• Disable X on the first and third weeks of the month, disable Y on the second and fourth weeks of the month.

Yep, there is no end to these “custom rules”. If I implement all of them, it won’t be a “simple date picker” anymore. So it’s up to you to do your own custom restrictions. Long story short –

• (A) Add your own custom restriction option to attach().
• (B) Modify draw() to also include your new restrictions.

 

 

DO SERVER-SIDE CHECKS!

Yes, the date picker is based on UTC+0, but “errors” still can happen. For you guys who are lost, the dates are based on the users’ devices. This can be easily changed, and potentially mess things up. So always do checks when the date/time is submitted, based on the server’s current time.

 

DATE RANGE PICKER

Sadly, this is another one that is “not simple”. Modify draw() and pick() if you wish. But otherwise, the easy way is to just create 2 date pickers – “Starting” and “until”. Upon submission, check that “until” is a later date than “starting”.

 

COMPATIBILITY CHECKS

• Arrow Functions – CanIUse
• Template Literals – CanIUse
• Viewport Units – CanIUse
• 2D CSS Transform – CanIUse

Works on all modern browsers. Not on the old Internet Exploders.