A simple calculator. You just need to enter an expression to calculate the result. This design mode is more convenient to operate.
For example: Enter "2*(3+6)+10/2.4", And click "Calculate" to get result. show result in console.
Support expression error detection.
For example: Enter "2*(3+6)+10/2.4+a12+100", and click "Calculate", will show error message in console.
Expression error！
Position: 2*(3+6)+10/2.4+a12+100
--------------------------^
Error: Illegal character
Support "+","-","x","/" and "(" operations.
