<!-- Learn about this code on MDN: https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault -->
<p>Please click on the checkbox control.</p>
<form>
<label for="id-checkbox">Checkbox:</label>
 <input type="checkbox" id="id-checkbox"/>
</form>
<div id="output-box"></div>
JavaScript
document.querySelector("#id-checkbox").addEventListener("click", function(event) {
event.preventDefault();
document.getElementById("output-box").innerHTML += "Sorry! <code>preventDefault()</code> won't let you check this!<br>";
}, false);
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