介绍

回文，亦称回环，是正读反读都能读通的句子，亦有将文字排列成圆圈者，是一种修辞方式和文字游戏。

实现

JavaScript

/*****************************************************************************
 * @function alphaNumericPlaindrome
 * @description alphaNumericPlaindrome should return true if the string has alphanumeric characters that are palindrome irrespective of special characters and the letter case.
 * @param {string} str the string to check
 * @returns {Boolean}
 * @see [Factorial](https://en.wikipedia.org/wiki/Palindrome)
 * @example
 * The function alphaNumericPlaindrome() receives a string with varying formats
 * like "racecar", "RaceCar", and "race CAR"
 * The string can also have special characters
 * like "2A3*3a2", "2A3 3a2", and "2_A3*3#A2"
 *
 * But the catch is, we have to check only if the alphanumeric characters
 * are palindrome i.e remove spaces, symbols, punctuations etc
 * and the case of the characters doesn't matter
 *
 ****************************************************************************/

const alphaNumericPlaindrome = (str) => {
  // removing all the special characters and turning everything to lowercase
  const newStr = str.replace(/[^a-zA-Z0-9]*/g, '').toLowerCase()

  for (let i = 0; i < newStr.length; i++) {
    if (newStr[i] !== newStr[newStr.length - 1 - i]) {
      return false
    }
  }

  return true
}

或者：

// Palindrome check is case sensitive; i.e. Aba is not a palindrome
// input is a string
const checkPalindrome = (str) => {
  // check that input is a string
  if (typeof str !== 'string') {
    return 'Not a string'
  }
  if (str.length === 0) {
    return 'Empty string'
  }
  // Reverse only works with array, thus convert the string to array, reverse it and convert back to string
  // return as palindrome if the reversed string is equal to the input string
  const reversed = [...str].reverse().join('')
  return str === reversed ? 'Palindrome' : 'Not a Palindrome'
}

参考

• 回文 - Wikiwand (opens new window)