javascript - Skipping parameters in callback function

Question

The callback function I'm working with has the following signature (from http://api.jquery.com/load/):

complete(responseText, textStatus, XMLHttpRequest)

Now, I only need the third parameter. In Lua there's a convention where an underscore is used to skip unneeded return values from functions (skip because _ will actually hold the value):

var1, _, _, var4 = func()

So I thought of doing a similar thing with JavaScript and set my function signature to this:

function (_, _, XMLHttpRequest)

Is there anything wrong with this approach, perhaps there's a better/cleaner way?

Answer 1

The technique is not pretty, but I use it myself on several occasions. I guess it is still quite better to give those unused arguments meaningful names (just to avoid confusion), but you're fine in using underscores.

I often see it used in jQuery related callbacks, where the index is often passed in as first argument, like

$('.foo').each(function(_, node) {
});

because most of the time, you don't care about the index there. So to answer your actual question, there is nothing wrong in using the technique (beside confusion maybe) and there is no better/cleaner way to skip unwanted arguments.