# What does (e:MouseEvent = null) mean?

**URL:** <https://forum.kirupa.com/t/what-does-e-mouseevent-null-mean/304037>\
**Category:** Uncategorized\
**Created:** [January 31, 2010, 2:56pm UTC](https://forum.kirupa.com/t/what-does-e-mouseevent-null-mean/304037 "2010-01-31T14:56:03Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![jeancnicolas](https://avatars.discourse-cdn.com/v4/letter/j/7bcc69/32.png) [@jeancnicolas](https://forum.kirupa.com/u/jeancnicolas)\
**Post date:** [January 31, 2010, 2:56pm UTC](https://forum.kirupa.com/t/what-does-e-mouseevent-null-mean/304037/1 "2010-01-31T14:56:03Z")

</div>

Hey … so im trying to work out some code :: and on this rollover state, I come across

```auto
private function onRollOver(e:MouseEvent):void {
			myFunction();
		}
private function myFunction(e:MouseEvent = null):void { }

```

… so what does this null mean? … or what is it doing …

Simple - but necessary thanks!