正则表达式禁止所有特殊字符，但允许德国变形金刚jQuery？

I would like to allow all Alphanumeric Characters and disallow all Special Characters in a RegEx. But I would like to allow German Umlauts but becouse they are Special Chars too, I can't type them in. I use this Script:I would like to allow all Alphanumeric Characte