LU07.S09 - Basic caluclator with methods

In LU06.S08 we were programming a basic calulator by manipulation the values directly when clicking the buttons. This is convenient, but limits the possibilities of the calculator significantly.

Therefore we need to do it, but this time by using a couple of methods

to set values of diggit1, diggit2 and the operator
to calulate the result
to reset all values of the variables

A01: Copy the solution of LU06.s07 and name it LU07.s09.html
A02: Make sure to have
- the assignmen number in <h1> and
- the description in <h3>-format
A03: Safe it.

B01: method setDiggit1(number): It sets the value of the variable diggit1 to the clicked number (diggit-block 1).
B02: method setDiggit2(number): It sets the value of the variable diggit2 to the clicked number (diggit-block 2).
B03: method setOperator(op): It sets the value of the variable operator to the clicked operation, e.g +. Hint: further operations are possible.
B04: method calcResult(op): Performes the calculation correspondigly to the chosen operation, e.g. +.
B05: method reset(): Sets all variables to the initial values.

C01: A basic calculation 3 + 3 = 6 compraises several variables and their initial values:
- diggit1: 0
- operator: ''
- diggit2: 0
- result: 0

D01: When clicking on one of them the content will be saved in the variable diggit1
D02: But unlike in the previous task, this time the click triggers a method setDiggit1(dig1)
D03: Continue with the other three buttons in the same fashion.
D04: Check the result by displaying the content of the variable diggit1 on the display.

E01: When clicking the +-button the content will be saved in the variable operator
E02: Check the result by displaying the content of the variable operator on the screen.

F01: When clicking on the button in diggit2-block, the content will be saved in the variable diggit2
F02: But unlike in the previous task, this time the click triggers a method setDiggit2(dig2)
F03: Continue with the other three buttons in the same fashion.
F04: Check the result by displaying the content of the variable diggit2 on the display.

G01: To execute our addition-operation we finally need a button ENTER. This triggers the method caldResult(operator)
G02: If the variable operator is an + (plus operator), then the calculation is an addition. In that case the result is this.result = diggit1 + diggit2. Hint: subtraktion, multiplication and division are similiar to programm.
G03: Display the result of the variable result on the screen.