My assumption is that it’s setting up an object to map element selectors -> callbacks.

var specialElementHandlers = {
  '#editor': function() {
    return true;
  }
};

But yeah, could be something as

var specialElementHandlers = Object.assign({}, defaultHandlers, {
  '#editor': function() {
    return true;
  }
}; // missing closing parenthesis 

You’re at a good age to do backpacking travel. Go explore the world.