javascript - alert when user attempts to enter key into textbox -

so i've been searching bit code alert user message (i know how alert) when try enter sort of text blank textbox.

here code. add cause sendmsg() function called?

<script>   function sendmsg()   {     alert ("change msg content here");   } </script>

here html:

<body>   <input type="text" name=""> </body>

this might work:

<input type="text" name="foo" onkeyup="sendmsg()" />

i.e. if understood question.

cheers.

Bready