how to fix element value in javascript on clicked code example

Example 1: button click function in js

<script>
  $(document).ready(function(){
    $('#MyButton').click(function(){
       CapacityChart();
    });
  });
</script>

<input type="button" value="Capacity Chart" id="MyButton" >

Example 2: javascript onclick

// The element id (TheElementID) and var name (myElement) can be named anything.
var myElement = document.getElementByID('TheElementID');
myElement.onclick = function() {
	// Carry out a function here...
}