检查是否是number类型,自动转换string类型

// 
module.exports = function isNumber (num) {
  // transform to number
  const number = +num
  // console.log(num, number)
  /**
   * Discard Infinity and NaN
   * Infinity,+Infinity,-Infinity => number - number = NaN
   * NaN => number - number = NaN
   * 这是不能通过number === number来判断,Infinity等于自身不符合。
   */
  if ((number - number) !== 0) {
    return false
  }
  if (typeof num === 'string') {
    /**
     * '   '
     * '\r\n\t'
     */
    if (number === 0 && num.trim() === '') {
      return false
    }
    return true
  }
  return true
}