code: function es5Fn(fn) {
    let s = fn.toString();
  
    //const name = fn.name;
  
    //if (s.startsWith('function (')) {
    //s = 'function ' + (name || '_fn' + nextFnName++) + ' (' + s.substring(10);
    /*} else */
    if (!s.startsWith('function')) {
      s = 'function ' + s;
    }
  
    return s;
  }
docs: let nextFnName = 1;