React Calculator Projec

1

Hey guys I was wondering if it is possible to make a regex for the calculator input with these conditions, the display starts with a 0 :

  • the fist char can be an + or - sign (optional)
  • if the first input is a . it should be appended to the 0
  • if the first input is a number it should take the place of the 0
  • the number can have only one .
  • after a number I can have an operator +-/*
  • the operator /* can be followed by an +-
  • if the input is an operator and the last char is a operator it should take the place of the last char

I could do that with a mix of regex and conditionals but i think it’s not the idea of a clean code:

  const displayPattern = /([+-]?)(\d+)(\.?)(\d*)([*/]?)([+-]?)/g;
  const isOperator = /[-+*/]/;
  const isNumber = /\d/;
  const isSign = /[-+]/;
  const lastChar = state.slice(-1);

if (value.includes('AC')) {
      setState('0');
    } else if (state.length === 1) {
      if (isNumber.test(value)) {
        if (state === '0') {
          setState(value);
        } else {
          setState(preVal => preVal + value);
        }
      } else if (value === '.') {
        setState(preVal => preVal + value);
      } else if (isSign.test(value)) {
        setState(value);
      }
    } else {
      if (isOperator.test(lastChar) && isOperator.test(value)) {
        if (isSign.test(lastChar)) {
          setState(prevVal => prevVal.slice(0, -1) + value);
        } else {
          !isSign.test(value) &&
            setState(prevVal => prevVal.slice(0, -1) + value);
        }
      }
      setState(
        preVal =>
          (preVal + value).match(displayPattern) &&
          (preVal + value).match(displayPattern).join('')
      );
    }