javascript button onclick

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

var button = document.querySelector('button');
button.onclick = function() {
  //do stuff
}

<button onclick="myFunction()">Click me</button>
 

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

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

 <input type="checkbox" id="myCheck" onmouseover="myFunction()" onclick="alert('clicked')">

 function myFunction() {
  document.getElementById("myCheck").click(); // Click on the checkbox
}