Get the variable Event 1

[seaport]

Many sample codes dealing with key stroke event have the first line of code as the following:

function KeyChecker(evt) {
evt = (evt) ? evt : ((event) ? event : null);
//some other code
}

I would just use

evt = (evt) ? evt : null

What is the code "(event) ? event : null" for?

My guess is that it is trying to get the variable from the document event rather than the form field event. Am I right?
In Firefox, if I just use "event" directly I will get an error.

Seaport

 

[trollacious]

If you expand your example to full if/else statements, you can see what it's doing better.

Lee

 

[tsuji]

>What is the code "(event) ? event : null" for?
It is the ie-specific event model. The event object is a global object under the window (omnipresence and optionally implicit). It is equivalent to a clearer (perhaps) version like this.
[tt] evt = (evt) ? evt : ((window.event) ? window.event : null);[/tt]
It is available only during an event on ie. Hence, the line check the implementation of event object (under window), if yes, re-assign evt to window.event. As such, cross-browser script is becoming possible using the same variable named evt even the content of it maybe very much different, moz vs ie.

 

[seaport]

Thanks, tsuji.

That line of code is for "cross-browser event accessing."

Here is what I found.

http://www.quirksmode.org/js/events_access.html

Seaport

 

[seaport]

By the way, tsuji, is there any rule about the position of the event parameter when defining a function in the Netscape event model?

For example, if the function to call requires 1 event variable - e, and 2 other variables. a and b, do I have to put the e as the last variable like

function testA(a,b,e)
{
//codes
}

or it does not matter at all?

Seaport

 

[tsuji]

Tacitly and in practice, it is usually the last. In case of no ambiguity, I would say at any position.

 

[seaport]

tsuji,

Thanks again.

Seaport