Not able to track enter key on input type = text

Can anybody tell me why is this not working?

  <input name ="txtChat" id ="txtChat" onkeydown ="isEnterPressed();"  type="text" style="width:720px;"/>

This is my javascript function :-

 function isEnterPressed(event){
                alert(event);

            }

On alert i always gets undefined :(

Thanks in advance :)

There is no built-in event type that is fired when the enter key is pressed, you need to check that in the Event object that is passed to the handler.

HTML:

<input name ="txtChat" id ="txtChat" onkeyup="onKeyPressed(event)"  type="text" style="width:720px;"/>

JavaScript:

function onKeyPressed(ev) {
   var e = ev || event;
   if(e.keyCode == 13) {
      //Enter was pressed
      return false; //prevents form from being submitted.
   }
}

A very simple inline check is:

<input name ="txtChat" id ="txtChat" onkeydown ="alert(event.keyCode == 13);"  type="text" style="width:720px;"/>

which outputs true if enter is pressed.