Finding longest palindrome (symmetric) substring in a string using Javascript (brute-force method)

longest_symmetric_substring.js

function longest_symm_substr(s) {
    let longest_symmetric = '';
  	for(let i=0;i<s.length-1;i++){ 
      // this loop will each time get a new substring incrementing the index from 0 to length
      let curr_str = s.substring(i); 
      for(let j=curr_str.length-1;j>0;j--){
        // this loop will find all possible symmetric substrings in the above indexed substring
        let str = curr_str.substring(0,j)
        if(str === str.split('').reverse().join('')){
          if(longest_symmetric.length < str.length){
            // keep record of the longest one
            longest_symmetric = str;
          }
        }
      }
    }
  return longest_symmetric;
}