Javascript String lastIndexOf(re, ndx)

String.prototype.lastIndexOf = function(re, ndx){
  let s = re.toString().replace(/\//g, '');
  if (ndx === undefined) ndx = this.length - 1;
  if (s[0] !== '^') s = '^' + s;
  else ndx = 0;//from   ww w  .  j a  v  a 2s .  co  m
  re = new RegExp(s, 'g');
  for (let i = ndx; i >= 0; i--) {
    const str = this.slice(i);
    if (re.test(str)) return i;
  }
  return -1;
};