JavaScript event IE issue when event is a global variable

I have a js function which accepts event object as an argument. In that js function, I assign that event object to a global variable. In another ajax callback I access that global variable (event object).

My Question开发者_运维技巧:

the key code value of that event in both methods are same in both methods in Firefox, but it gives different value in IE 7? for example,if key code is 75, Firefox returns 75 in both methods. but IE7 gives 75 in method-1 and 0 in method-2

Why does it behave like this?

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You can not pass the event object with IE, you need to create a new object and make a copy the properties that you want to use.