Answers for "how to define onclick function in javascript"

javascript button onclick

document.getElementById('button').onclick = function() {
   alert("button was clicked");
};

button click function in js

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

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

html js button onclick

// In HTML:
// <button id="buttonID" onclick="yourJSFunction()">Text</button>

// In JavaScript:
function yourJSFunction() {
  // Do stuff
 }