Defining JavaScript Event Object

Question

Why am I getting an error for this piece of code?:

function catchevent() 
{
    eventSrcID=(event.srcElement)?event.srcElement.id:\'undefined\';

    eventty         


        

Answer 1

The event object is a global variable in internet explorer. (Actually a property of the global window variable)

Firefox is simply a different design, and event is not a global variable in firefox. Instead, it is passed into the function (so you would need to change catchEvent() to accept a parameter:

function catchEvent(event){

Take a look at this artice because that is not the only problem you'll face with the event model:

http://www.quirksmode.org/js/introevents.htmlQuirksmode article

Answer 2

In Firefox and other W3C compliant browsers, the handler function will receive an event object as an argument to the function.

IE uses a global event object.

Here's a cross browser solution for your code.

function catchevent( e ) {
      // reference the proper event object
    var e = e || window.event;

      // reference the proper target
    var srcElem = e.target || e.srcElement;

      // get the id of the target
    var eventSrcID = srcElem.id;

      // get the event type
    var eventtype = e.type;

      // create the status string
    var status = eventSrcID + ' has received a ' + eventtype + ' event.';
}

You'll notice I used the var keyword when creating variables. You should do this, otherwise you're creating global variables.

Also note that the keyword this will be a reference to the element to which the handler was assigned.

Answer 3

In Firefox, the first param passed to a handler is the event. So a cross browser piece of code would check for a param and use it if present. If not present, it would default to window.event, the IE way.

Answer 4

you forgot to pass event in parameters.

function catchevent(event) 
{
    eventSrcID=(event.srcElement)?event.srcElement.id:'undefined';

    eventtype=event.type;

    status=eventSrcID+' has received a '+eventtype+' event.';
}