execcommand javascript
<!DOCTYPE html>
<html>
<body onkeydown="myFunction(event)">
<h1>The Document Object</h1>
<h2>The execCommand() Method</h2>
<p>The executeCommand() method executes a specified command on selected text.</p>
<p>Select some text in this page, and press SHIFT to make the selected text toggle between bold and normal.</p>
<script>
document.designMode = "on";
function myFunction(event) {
if (event.keyCode == 16) {
// Execute command if user presses the SHIFT button:
document.execCommand("bold");
}
}
//From https://www.w3schools.com/jsref/met_document_execcommand.asp
</script>
</body>
</html>