不能在 Mozilla or Firefox 下运行的JavaScript

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Today I finded some JavaScritp can not normal work in the FrieFox

like KeyEncode

IE
    onkeypress="return event.keyCode>=48 && event.keyCode<=57 || event.keyCode==46"

But It's don't work in the Firefox  at Firefox you need Change

FireFox
    <html:text property="shipDate"  maxlength="8" size="20" onfocus="javascript:pass=1;" onblur="javascript:pass=null;" />

var pass;
    function vtbKeyPress(e)
    {
        if (!pass){return;}
        if (!document.all) {
            KeyCode=e.which;
        } else{
            KeyCode=event.keyCode; // Demo Only
        }
        return KeyCode>=48 && KeyCode<=57 || KeyCode==8;
    }
        if (!document.all){document.captureEvents(Event.KEYDOWN)}
        document.onkeypress=vtbKeyPress