Check out a free preview of the full ES6: The Right Parts course:
The "Dumping Variables" Lesson is part of the full, ES6: The Right Parts course featured in this preview video. Here's what you'd learn in this lesson:

Kyle spends a few minutes talking about a technique for dumping variables through destructuring. He uses empty slots in an array to “catch” the variables to be dumped. He then uses the gather operator to populate the original variable with the remaining destructured values.

Get Unlimited Access Now

Transcript from the "Dumping Variables" Lesson

[00:00:00]
>> [MUSIC]

[00:00:03]
>> Kyle Simpson: So, if we know that we can receive assignments without declaration. We can also do an interesting little trick, it's just a little side note, it's not something I'm doing an awful lot. But you remember earlier, when we we're talking about using block scoping to do that whole swapping thing.

[00:00:24] Remember we did let tmp = x; x =y; y = tmp. Remember that? We can use array de-structuring to do the swapping. Let's say I had an x = 10. And a y that was 20 and I wanted to swap the two. Could do that whole block thing that I just showed.

[00:00:44] Or what I could do is say, an array de-structuring with x and y as my pattern should be de-structured from an array that has them in the opposite order.
>> Kyle Simpson: And of course that's not limited to two. You could do as many of those as you wanted to, right?

[00:01:17]
>> Kyle Simpson: While we're on the topic of using this array de-structuring stuff, If we had an a that was an array like that.
>> Kyle Simpson: We could say, for example.
>> Kyle Simpson: So, now we're making an array, a composite array, I'll use spaces just to make this a little more readable.

[00:01:44] We now have an array on the right hand side, that has zero through four in it, right? And over here we could say, I want to throw away the first two of these. We're going to have to make variables to catch those, collect the rest of them right back into a.

[00:02:01] So, that is the effect of throwing away zero and one, and now a is going to have two three four in it, okay? Remember our whole usage of dot, dot, dot operator? It also works with our de-structuring. So, now we see the dot, dot, dot on both sides.

[00:02:15] One on the right hand side it's doing spreading. On the left hand side it's doing gathering.
>> Kyle Simpson: And we could just have a single variable here, like that or underscore, or whatever other one you wanted to use to say, this is just, I'm just dumping these I don't care about, okay?

[00:02:36]
>> Kyle Simpson: But you don't even need that, because the array de-structuring allows you to do empty slots.
>> Kyle Simpson: So, now if we ran this example, our a would be an array that had values two three and four in it. Zero and one would have been done, okay? So, we can use our pattern de-structuring and even more, I don't necessarily want to call it a tricky way, but we can use the capabilities of it to take on tasks that would have been a lot more ugly to express in imperative form.

[00:03:16]
>> Speaker 2: So, I take it if you transpired that it would just give it some random variable names that never get used again? On those two that get tossed up.
>> Speaker 2: It just slices instead.
>> Kyle Simpson: See they're doing all this analysis to figure out what's the simplest path, used characters, most performant to get it.

[00:03:41] So, you might say, this is how I would do it I'd make these temporary variables or whatever, and they're saying we've all ready analyzed and figured out this is the best way to do it.
>> Speaker 2: So, with the empty slots just the white space matter, or is it just [CROSSTALK]

[00:03:55]
>> Kyle Simpson: I do that for readability, it doesn't matter at all.
>> Kyle Simpson: There's the array with two, three, four in it.