The error message indicates that the element countdown is missing or does not exist

Question

The error message indicates that the element countdown is missing or does not exist

I typically refrain from discussing topics that I'm not well-versed in (my weak spot has always been working with time and dates in javascript), but I find myself in urgent need of assistance.

I've decided to use this link to showcase a countdown timer on my client's website. It seems like a simple task, right? Here's how I implemented it:

<script type="text/javascript">
// set the date we're counting down to
var target_date = new Date('Sep, 18, 2015').getTime();

// variables for time units
var days, hours, minutes, seconds;

// get tag element
var countdown = document.getElementById('countdown');

// update the tag with id "countdown" every 1 second
setInterval(function () {

    // determine the number of "seconds" between now and the target
    var current_date = new Date().getTime();
    var seconds_left = (target_date - current_date) / 1000;

    // perform some time calculations
    days = parseInt(seconds_left / 86400);
    seconds_left = seconds_left % 86400;

    hours = parseInt(seconds_left / 3600);
    seconds_left = seconds_left % 3600;

    minutes = parseInt(seconds_left / 60);
    seconds = parseInt(seconds_left % 60);

    // format the countdown string and set the tag value
    countdown.innerHTML = '<span class="days">' + days + ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
    + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

}, 1000);
</script>

Style

<style>
.container {
  margin: 0px auto;
  padding: 0px;
}

#main { 
  background: #3B3B3B;
  height: 430px;
}

.content {
  padding: 10px 44px;
}

.text {
  border-bottom: 1px solid #262626;
  margin-top: 40px;
  padding-bottom: 40px;
  text-align: center;
}

.text h2 {
  color: #E5E5E5;
  font-size: 30px;
  font-style: normal;
  font-variant: normal;
  font-weight: lighter;
  letter-spacing: 2px;
}

.counter {
  background: #2C2C2C;
  -moz-box-shadow: inset 0 0 5px #000000;
  -webkit-box-shadow: inset 0 0 5px #000000;
  box-shadow: inset 0 0 5px #000000;
  min-height: 150px;
  text-align: center;
}

.counter h3 {
  color: #E5E5E5;
  font-size: 14px;
  font-style: normal;
  font-variant: normal;
  font-weight: lighter;
  letter-spacing: 1px;
  padding-top: 20px;
  margin-bottom: 30px;
}

#countdown {
  color: #FFFFFF;
}

#countdown span {
  color: #E5E5E5;
  font-size: 26px;
  font-weight: normal;
  margin-left: 20px;
  margin-right: 20px;
  text-align: center;
}
</style>

HTML

<div class="container">
<div class="row">
<div class="col-lg-12 col-md-12 col-sm-12 col-xs-12">
<div id="main">
<div class="content">
<div class="text">
<h2>This Website Is Under Construction</h2>
</div><!-- /.Text Div -->
<div class="counter">
<h3>Estimated Time Remaining Before Launch:</h3>
<div id="countdown">
</div><!-- /#Countdown Div -->
</div><!-- /.Counter Div -->
</div> <-- /.Content Div -->
</div> <-- /#Main Div -->
</div> <-- /.Columns Div -->
</div> <-- /.Row Div -->
</div> <-- /.Container Div -->

Output

https://i.sstatic.net/hR88B.png

Firefox throws the following error:

https://i.sstatic.net/v3SpF.png

Chrome displays the following message:

https://i.sstatic.net/xdWqw.png

The code is identical to what I have provided above, yet I encounter the errors shown in the images attached. Interestingly enough, when using this fiddle I have created, everything works fine. Quite perplexing, don't you think?

javascript jquery html css

Answer 1

Answer №1

Ensuring that your code runs after the document has fully loaded is crucial. Otherwise, the element with the ID may not exist yet when the code executes. In your case, the countdown variable will be null because the element hasn't been added to the document at the time of execution.

An easy workaround, as seen in your jsfiddle example (look at the source in the bottom right frame), is to place the <script> tag below the element so that the countdown element will likely exist when the code runs.

A more robust solution, especially since you have tagged your question with jQuery, would be to encapsulate your code within $(document).ready() or its shorthand:

$(function() {
  // Your code...
});

If compatibility with IE8 and below is not a concern, there is also a Vanilla JS alternative that you can consider.

Below is a runnable snippet showcasing the jQuery solution:

$(function() {
  var target_date = new Date('Sep, 18, 2015').getTime();
  var days, hours, minutes, seconds;
  var countdown = document.getElementById('countdown');

  setInterval(function () {

    // calculate the "seconds" remaining until the target date
    var current_date = new Date().getTime();
    var seconds_left = (target_date - current_date) / 1000;

    // perform time calculations
    days = parseInt(seconds_left / 86400);
    seconds_left = seconds_left % 86400;

    hours = parseInt(seconds_left / 3600);
    seconds_left = seconds_left % 3600;

    minutes = parseInt(seconds_left / 60);
    seconds = parseInt(seconds_left % 60);

    // format the countdown string and update the element's value
    countdown.innerHTML = '<span class="days">' + days +  ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
    + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

  }, 1000);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<h3>Estimated Time Remaining Before Launch:</h3>
<div id="countdown"></div>

Here is another version that ensures the counter starts immediately instead of waiting for the first 1-second interval:

$(function() {
  var target_date = new Date('Sep, 18, 2015').getTime();
  var days, hours, minutes, seconds;
  var countdown = document.getElementById('countdown');

  function updateCounter() {

    // find the amount of "seconds" between now and target
    var current_date = new Date().getTime();
    var seconds_left = (target_date - current_date) / 1000;

    // do some time calculations
    days = parseInt(seconds_left / 86400);
    seconds_left = seconds_left % 86400;

    hours = parseInt(seconds_left / 3600);
    seconds_left = seconds_left % 3600;

    minutes = parseInt(seconds_left / 60);
    seconds = parseInt(seconds_left % 60);

    // format countdown string + set tag value
    countdown.innerHTML = '<span class="days">' + days +  ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
    + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

  }
  
  updateCounter();
  
  setInterval(updateCounter, 1000);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<h3>Estimated Time Remaining Before Launch:</h3>
<div id="countdown"></div>

Answer 2

Ensuring that your code runs after the document has fully loaded is crucial. Otherwise, the element with the ID may not exist yet when the code executes. In your case, the countdown variable will be null because the element hasn't been added to the document at the time of execution.

An easy workaround, as seen in your jsfiddle example (look at the source in the bottom right frame), is to place the <script> tag below the element so that the countdown element will likely exist when the code runs.

A more robust solution, especially since you have tagged your question with jQuery, would be to encapsulate your code within $(document).ready() or its shorthand:

$(function() {
  // Your code...
});

If compatibility with IE8 and below is not a concern, there is also a Vanilla JS alternative that you can consider.

Below is a runnable snippet showcasing the jQuery solution:

$(function() {
  var target_date = new Date('Sep, 18, 2015').getTime();
  var days, hours, minutes, seconds;
  var countdown = document.getElementById('countdown');

  setInterval(function () {

    // calculate the "seconds" remaining until the target date
    var current_date = new Date().getTime();
    var seconds_left = (target_date - current_date) / 1000;

    // perform time calculations
    days = parseInt(seconds_left / 86400);
    seconds_left = seconds_left % 86400;

    hours = parseInt(seconds_left / 3600);
    seconds_left = seconds_left % 3600;

    minutes = parseInt(seconds_left / 60);
    seconds = parseInt(seconds_left % 60);

    // format the countdown string and update the element's value
    countdown.innerHTML = '<span class="days">' + days +  ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
    + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

  }, 1000);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<h3>Estimated Time Remaining Before Launch:</h3>
<div id="countdown"></div>

Here is another version that ensures the counter starts immediately instead of waiting for the first 1-second interval:

$(function() {
  var target_date = new Date('Sep, 18, 2015').getTime();
  var days, hours, minutes, seconds;
  var countdown = document.getElementById('countdown');

  function updateCounter() {

    // find the amount of "seconds" between now and target
    var current_date = new Date().getTime();
    var seconds_left = (target_date - current_date) / 1000;

    // do some time calculations
    days = parseInt(seconds_left / 86400);
    seconds_left = seconds_left % 86400;

    hours = parseInt(seconds_left / 3600);
    seconds_left = seconds_left % 3600;

    minutes = parseInt(seconds_left / 60);
    seconds = parseInt(seconds_left % 60);

    // format countdown string + set tag value
    countdown.innerHTML = '<span class="days">' + days +  ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
    + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

  }
  
  updateCounter();
  
  setInterval(updateCounter, 1000);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<h3>Estimated Time Remaining Before Launch:</h3>
<div id="countdown"></div>

Answer 3

Answer №2

Is the JavaScript code being triggered after the document has finished loading? It appears you are trying to access a DOM element with the ID countdown, but it may not have been rendered yet.

Check out jQuery's document ready function for guidance.

In general, your code should resemble this:

    $( document ).ready(function() 
    {
        var target_date = new Date('Sep, 18, 2015').getTime();

        // variables for time units
        var days, hours, minutes, seconds;

        // get reference to the countdown element
        var countdown = document.getElementById('countdown');

        ... //etc...
    });

Answer 4

Is the JavaScript code being triggered after the document has finished loading? It appears you are trying to access a DOM element with the ID countdown, but it may not have been rendered yet.

Check out jQuery's document ready function for guidance.

In general, your code should resemble this:

    $( document ).ready(function() 
    {
        var target_date = new Date('Sep, 18, 2015').getTime();

        // variables for time units
        var days, hours, minutes, seconds;

        // get reference to the countdown element
        var countdown = document.getElementById('countdown');

        ... //etc...
    });

Answer 5

Answer №3

If you prefer not to use jQuery in this case, consider wrapping your setInterval method with a startCount function and triggering it with the body's onload event.

function startCount() {

    // update the tag with id "countdown" every 1 second
    setInterval(function () {

        // determine the number of seconds remaining until the target date
        var current_date = new Date().getTime();
        var seconds_left = (target_date - current_date) / 1000;

        // perform time calculations
        days = parseInt(seconds_left / 86400);
        seconds_left = seconds_left % 86400;

        hours = parseInt(seconds_left / 3600);
        seconds_left = seconds_left % 3600;

        minutes = parseInt(seconds_left / 60);
        seconds = parseInt(seconds_left % 60);

        // format countdown string + update tag value
        countdown.innerHTML = '<span class="days">' + days +  ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
        + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

    }, 1000);

}

Include the following code in the body tag:

<body onload='startCount();'>

Answer 6

If you prefer not to use jQuery in this case, consider wrapping your setInterval method with a startCount function and triggering it with the body's onload event.

function startCount() {

    // update the tag with id "countdown" every 1 second
    setInterval(function () {

        // determine the number of seconds remaining until the target date
        var current_date = new Date().getTime();
        var seconds_left = (target_date - current_date) / 1000;

        // perform time calculations
        days = parseInt(seconds_left / 86400);
        seconds_left = seconds_left % 86400;

        hours = parseInt(seconds_left / 3600);
        seconds_left = seconds_left % 3600;

        minutes = parseInt(seconds_left / 60);
        seconds = parseInt(seconds_left % 60);

        // format countdown string + update tag value
        countdown.innerHTML = '<span class="days">' + days +  ' <b>Days</b></span> <span class="hours">' + hours + ' <b>Hours</b></span> <span class="minutes">'
        + minutes + ' <b>Minutes</b></span> <span class="seconds">' + seconds + ' <b>Seconds</b></span>';  

    }, 1000);

}

Include the following code in the body tag:

<body onload='startCount();'>

The error message indicates that the element countdown is missing or does not exist

Answer №1

Answer №2

Answer №3

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