Project: "Calculator"

A common calculator. It is strange for me, in courses I have been through, there was no any code of a calculator. It seems made directly, for using in some course for begginers (There was one calculator, but it was made in the Flex only, widthout javaScript code). I used the evaluate() method, I found it in the web, not in the courses. I had a problem width bacspace, on keyboard, but now it works quite ok. Still there is a problem width using keyboard width the calculator. The keyboard signs, are written in double... I haven't resolve the problem yet.