JS HTML Objects
HTML elements expose specialised properties as well as general DOM methods. A checkbox checked property holds its current boolean state.
Where to run this
This example changes a document. Open it in the HTML playground, then select Run code. It runs inside a separate preview.
A practical example
<label><input id="updates" type="checkbox">Send updates</label>
<p id="result"></p>
<script>
document.getElementById("updates").addEventListener("change", event => {
document.getElementById("result").textContent = event.target.checked ? "Updates selected" : "Updates off";
});
</script>
What happens
The message follows the checkbox current state.