Terning On a Control

One of Tim‘s co-workers needed to handle a simple condition: if a control in their web app was enabled, show it, otherwise hide it.

Now, if you or I were writing that, we might write some awfully verbose code, like:

if (on)
{
	d.show();
}
else
{
	d.hide();
}

It’s an obvious solution, and while there are probably better ways to structure the program, it’s a perfectly viable approach. But only a weak, underskilled programmer would want to do the obvious thing. Tim’s co-worker wants you to know that they’re clever, so they wrote it this way:

d[on?'show':'hide']();

This is a “clever” abuse of a “feature” of JavaScript: all objects are really just maps. The ternary chooses a key: if we’re on, use the key show, otherwise use the key hide. Then we invoke the function at that key.

No one changed the code to make it more clear- it’s spammed all over the codebase- but they did add a comment everywhere this pattern appeared, just to avoid future confusion.