unshift
Adding data to an array. now that we know how to push we need to know how to do it from the other end.
Video Transcript
00:00The next thing I want to do is see what it would be if we didn't want to push.
00:04What if we wanted to add a user to the top of the list?
00:07As we said, a raise or an index, and there's a priority in their order.
00:11And Cyrus is, for example, my boss.
00:13And thus, Cyrus is supposed to come first.
00:16Well, Sarah is not a boss.
00:18She's just a more junior employee.
00:20And for some reason, we want to sort our users not only by their membership level,
00:24but also by their seniority.
00:26So now, because Cyrus joined in first, let's just delete early.
00:30And let's just comment this out, right?
00:32We're just going to comment this out.
00:33And let's just add Sarah again to the end of the list.
00:38A users dot push.
00:40And we've seen that already.
00:41So we're going to send Sarah to the end of the list, as we've seen before.
00:44And now, if we want to put Cyrus to be the first in the list,
00:48the way we would do that in Flash is called unshift.
00:51And we're going to see in a minute what shift means.
00:53But if we want to call unshift, a users dot unshift,
00:57an unshift again could accept multiple parameters.
01:00But in arson hour, we're just going to use one, which will be Cyrus.
01:03And look what's going to happen here.
01:06First of all, our original array we're going to output,
01:08which is basically what you see right here.
01:10In the first line, we're adding to the end of the list.
01:13We're adding Sarah to the end of the list by pushing her to the end.
01:16And then we're unshifting Cyrus to the beginning of the array.
01:20Thus, we should see Cyrus in the beginning of the array.
01:22And Sarah should be in the end of the array.
01:24So if we run our application one more time now,
01:27we should now see that Cyrus is in the beginning of the list
01:30because we used unshift.
01:32And Sarah is in the end of the list.
01:34Now, let me just ask you a hypothetical question.
01:36What would happen if I would take this item and move it up?
01:39Would it matter?
01:40And the answer is right now, no, it wouldn't,
01:42because we're first pushing this to the beginning,
01:44and then we're pushing this item to the end.
01:46Although if we would push and then push again,
01:50there would definitely be a difference.
01:51Or if we would unshift and then unshift again,
01:53there would be a big difference.
01:55Because right now, this would be pushed to the first.
01:57But if we unshift again, let's do that.
02:00If I unshift, and let's say we have another manager,
02:03and his name is Bart.
02:04And we unshift Bart.
02:07Now, Bart will be first.
02:09So Cyrus was first in line 13.
02:11But as soon as we finish line 13, line 14 already
02:15is pushing Bart to be first.
02:16So if we run our application one more time again,
02:18we're going to see that Bart now is first
02:20and Cyrus is second.
02:21And same is true with pushing more items
02:24to the end of the list.
02:25So if I push, let's say, if we push Marge
02:31to the end of the list, then we'll
02:33see that Marge will be in the end of the list after Sarah.
02:36And it's very important not to forget this
02:38because you might find yourself in some messy bugs.
02:42If you don't realize the difference between unshift
02:44and push and making sure that you
02:46know the importance of the priority.
02:48So now if I change the order now, obviously,
02:50Marge will be first.
02:51And only after that, Sarah would come.
02:54So these are really important.
02:56And it goes back to these basic foundations
02:59of arrays, which is our last complex object
03:01that we're learning about in the basic,
03:04native, getting started learning programming.
03:08So this is very exciting.