How to check if a value isn't changed in between <span> tag

The page looks like:

<html>
  <span id="somespan">1000</span>
</html>

The value of somespan increases every 1 or 2 minutes.

With Javascript/JQuery, how can I check if the value is same or increased every 5 minutes.

I mean at 16:00 the value is 1000 and 2 minutes later so at 16:02 its 1200.
How can I check if its changed.

I wanna make something like:

var somespan = $("#somespan").text();

if(somespan isnt changed) {
  #console.log('still same.')    
}

The platform i will use this code is Google Chrome -> Tampermonkey

Solution

You can implement a MutationObserver, but this will do as well.

var current_value = null;
setInterval( function() {
  if (current_value != null) {
    if (current_value != $('#somespan').text()) {
      console.log('Value has changed!');
    }
  }
  current_value = $('#somespan').text();
}, 1000 );

// For testing only
$('input').on('input', function() {
  $('#somespan').text( $(this).val() );
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<span id="somespan">1000</span>

<!-- For testing only -->
<br/>
<input type="text" value="1000">

via MutationObserver (no polling required)

const observer = new MutationObserver(function(mutations) {
  for (const mutation of mutations) {
    if (mutation.type === 'childList') {
      console.log('Value has changed!')
    }
  }
});

observer.observe(document.querySelector('#somespan'), {childList: true});

// For testing only
document.querySelector('input').addEventListener('input', function() {
  document.querySelector('#somespan').innerHTML = this.value;
});

<span id="somespan">1000</span>

<!-- For testing only -->
<br/>
<input type="text" value="1000">