Yup validate input for too many decimals to prevent ethers.js BigNumber / BigInt underflow

yup.ts

let decimals = 4;
const regexpDecimals = new RegExp(`^\\d*\\.{0,1}\\d{0,${decimals}}$`);

const SignupSchema = Yup.object().shape({
  decimal: Yup.number().test(
    'is-decimal',
    'too many decimals',
    value => (value + "").match(regexpDecimals),
  ),
});

// Test cases
"424324.123456".match(new RegExp(`^\\d*\\.{0,1}\\d{0,6}$`));
"424324".match(new RegExp(`^\\d*\\.{0,1}\\d{0,6}$`));