Create dispatchEvent Vanilla JS

createEvent-dispatchEvent and preventDefault

// Markup
<input type="checkbox" id="checkbox"/><label for="checkbox">Checkbox</label>
Simulate click	<input type="button" onclick="simulateClick();" value="Simulate click"/>
Add a click handler that calls preventDefault	<input type="button" onclick="addHandler();" value="Add a click handler that calls preventDefault"/>
Remove the click handler that calls preventDefault	<input type="button" onclick="removeHandler();" value="Remove the click handler that calls preventDefault"/>

// Script

var checkbox = document.querySelector('.checkbox')

function preventDef(event) {
  event.preventDefault();
};

function addHandler() {
  checkbox.addEventListener('click', preventDef, false);
};

function removeHandler() {
  checkbox.removeEventListener('click', preventDef, false);
};

function simulateClick() {
  var event = new MouseEvent('click', {
    view: window,
    bubbles: true,
    cancelable: true
  });
  var cb = document.getElementById('checkbox'); 
  var cancelled = !cb.dispatchEvent(event);
  if (cancelled) {
    // A handler called preventDefault.
    alert("cancelled");
  } else {
    // None of the handlers called preventDefault.
    alert("not cancelled");
  }
}