Question

I would like a function ‘get’ that takes an id, an optional property parameter and a callback function. It would be used like so:

get(14297, 'name', function processName(name) {...});
get(14297, function processStudent(student) {...});

I have included one possible implementation below

function get(id, property, callback) {
    var item = ...;
    // property is callback
    if (!callback) property(item);
    // callback is callback
    else callback(item[property])
}

It feels a little bit weird because

property(item);

Is actually a callback function depending on the context. Is there a better way to do this?

Answer 1

You can change the order of parameters, or test what the function is given to work out what they are. e.g.

function get(id, property, callback) {
  if (arguments.length == 2) {
    // second argument is callback
    callback = property;
    property = void 0;
  }
  ...
}

or

function get(id, property, callback) {
  if (typeof property == 'function') {
    // second argument is callback
    callback = property;
    property = void 0;
  }
  ...
}

and so on, but that type of overloading is not particularly liked.