Unwanted sharing of variables inside class functions

[Sorccu]

Let's go directly to the code:

<script language="JavaScript" type="text/javascript">
var MyClass = {
	Method : function(num) {
		a = num; // a = 2
		someValueINeed = MyClass.AnotherMethod(10); 
		alert(a); // now a = 10! wtf?
	},
	AnotherMethod : function(someNum) {
		a = someNum;
		return a;
	}
};
MyClass.Method(2);
</script>

The code above is an example of the problem and should be very self-explaining. The vars of AnotherMethod overwrite the vars of Method, which was called first. I have no idea why this happens, and I really don't want it to happen. Renaming the variables helps, but it is a very, very poor solution and does not work when recursing a function as follows:

<script language="JavaScript" type="text/javascript">
var MyClass = {
	Method : function(num,preventEndlessRecursion) {
		a = num;
		if (preventEndlessRecursion) { // prevent endless loop :)
			MyClass.Method(5);
			alert(a); // a = 5! again, wtf?
		}
	}
};
MyClass.Method(2,true);
</script>

Now, if you have ANY idea how to prevent this from happening, PLEASE tell me. It'd be greatly appreciated.

[FauxPas]

Try using var to declare separate variables:

var MyClass = {
	Method : function(num) {
		var a = num; // a = 2
		someValueINeed = MyClass.AnotherMethod(10); 
		alert(a); // now a = 10! wtf?
	},
	AnotherMethod : function(someNum) {
		var a = someNum;
		return a;
	}
};
MyClass.Method(2);

[Sorccu]

Yes! Great, thanks! Reputation on it's way