vant/src-next/utils/validate/number.ts

export function isNumeric(val: string): boolean {
  return /^\d+(\.\d+)?$/.test(val);
}

export function isNaN(val: number): val is typeof NaN {
  if (Number.isNaN) {
    return Number.isNaN(val);
  }

  // eslint-disable-next-line no-self-compare
  return val !== val;
}