Duplicated Argument Names

Oftentimes we override or monkey patch functions and, in many cases, there are arguments we don't care too much about. A common practice for those arguments is using _ for argument names -- it's a generally accepted and known practice for "this isn't important". I started thinking about multiple useless arguments and if you could use the same name for the sake of minification -- you can.

So what happens when you use the same argument name more than once? An error? Uses the first value? The last value? Let's have a look:

function myFunc(_, _, _) {
  console.log("_: ", _);
}

myFunc(1, 2, 3);

// >> 3

The duplicated argument is given the value of the last provided argument. If, however, "use strict" is used, an error will be thrown.

For some reason I expected an error when using an argument name more than once. On the other end, you can change argument values so I shouldn't be surprised. Anyway, happy coding!