execute command method
<!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>