js回文数的4种判断方法示例

/
  @param {number} x
  @return {boolean}
 /
var isPalindrome = function(x) {
  if ( x < 0 ) return false
  let str = '' + x
  return Array.from(str).reverse().join('') === str
};

/
  @param {number} x
  @return {boolean}
 /
var isPalindrome = function(x) {
  let str = x + ''
  let newStr = ''
  for(let len = str.length, i = len - 1; i >= 0 ; i--) {
    newStr += str[i]
  }}
  return newStr === str
};

/
  以中间数为节点，判断左右两边首尾是否相等
  @param {number} x
  @return {boolean}
 /
var isPalindrome = function(x) {
  if ( x < 0 || (x !== 0 && x % 10 === 0)) {
    return false
  } else if ( 0 <= x && x < 10) {
    return true
  }
  x = '' + x
  for(let i = 0 ; i < x.length/2; i++) {
    if (x[i] !== x[x.length - i - 1]) {
      return false
    }
  }
  return true
};

/
  求模得尾数，除10得整数
  @param {number} x
  @return {boolean}
 /
var isPalindrome = function(x) {
  if ( x < 0 || (x !== 0 && x % 10 === 0)) {
    return false
  } else if ( 0 <= x && x < 10) {
    return true
  }
  let y = x
  let num = 0
  while(x !== 0) {
    num = x % 10 + num  10
    x = Math.floor(x / 10)
  }
  return y === num
};