index.js
function(s) {
      var r = '';
      for (var i = s.length - 1; i >= 0; i--) {
        r += s[i];
      }
      return r;
    }
function(s) {
      var r = '';
      for (var i = s.length - 1; i >= 0; i--) {
        r += s[i];
      }
      return r;
    }
function ( s ) { var r = '' ; for ( var i = s . length - 1 ; i >= 0 ; i -- ) { r += s [ i ] ; } return r ; }
javascript doesn't have negative lookbehind so we have to reverse the string
javascript doesn t have negative lookbehind so we have to reverse the string