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<!DOCTYPE html> <html> <body> <p>This example uses the HTML DOM to assign an "onkeydown" event to an input element.</p> <p>Press a key inside the text field to set a red background color.</p> <input type="text" id="demo"> <script> document.getElementById("demo").onkeydown = function() {myFunction()}; function myFunction() { document.getElementById("demo").style.backgroundColor = "red"; } </script> </body> </html>