<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <script type="text/javascript"> function prompter(defaultval) { var reply = prompt("js prompt", defaultval); console.log("Prompt reply: " + reply); } </script> </head> <body> <input type="button" onclick="prompter('')" value="Show prompt" id="button"> <input type="button" onclick="prompter('default')" value="Show prompt with default value" id="button-default"> </body> </html>