JS judge palindromes

Judge the palindrome number

Form of array inversion

/** *  Form of array inversion  */
function findNums1(num){
    
  const res = []
  for(let i=1;i<=num;i++){
    
    const s = i.toString()
    if(s===s.split('').reverse().join('')){
    
      res.push(i)
    }
  }
  return res
}

Compare the beginning and end of the string

/** *  Compare the beginning and end of the string  */
 function findNums2(num){
    
  const res = []
  for(let i=1;i<=num;i++){
    
    const s = i.toString()
    const length = s.length

    //  Compare the beginning and end of the string 
    let flag = true
    let start = 0 // String start 
    let end = length-1 // End of string 
    while(start < end){
    
      if(s[start] !== s[end]){
    
        flag = false
        break
      }else {
    
        //  Continue to compare 
        start++
        end--
      }
    }
    if(flag) res.push(i)
  }
  return res
}

Pure digital comparison

/** *  Pure digital comparison  */
 function findNums3(num){
    
  const res = []
  for(let i=1;i<=num;i++){
    
    let n = i
    let rev = 0 // Store the reverse rotation number 

    //  Generate inversion number 
    while(n>0){
    
      rev = rev*10+n%10
      n = Math.floor(n/10)
    }

    if(i===rev) res.push(i)
  }
  return res
}

The performance is getting better and better from top to bottom