Arrays

Quick reference

• 00:05 Okay, we've already talked about variables.
• 00:06 In this video, I wanna talk about arrays.
• 00:08 And arrays are just incredibly important to any programming language.
• 00:12 And they're really sort of the beginning of more intermediate programming stuff.
• 00:17 We've been talking about basic stuff up until now.
• 00:19 Arrays, we're starting to get into more advanced stuff.
• 00:21 They're just one of those fundamental things that all programming languages
• 00:24 have, and you're gonna use them a lot.
• 00:26 So if a variable is a container, or
• 00:28 a bucket, that holds one thing, an array is a container that holds lots of things.
• 00:33 In fact, they'll hold as many things as you can cram in there.
• 00:36 And you can keep putting things in, and you can take things out.
• 00:39 And you can do all kinds of things.
• 00:40 So they're great for
• 00:41 storing lists of things like lists of names or customer phone numbers or
• 00:46 email addresses or anything you want, pizza toppings, it doesn't really matter.
• 00:50 So, how do we make an array in JavaScript?
• 00:52 Well, it's pretty easy, and it looks a lot like a variable.
• 00:55 So if we come up here, we can go, var, we're gonna declare it, give it a name.
• 01:00 Let's call it pizza and equals to.
• 01:02 Up until now it looks just like a variable.
• 01:04 Now we use these brackets.
• 01:06 And every item we wanna put into the array we just put quotations around.
• 01:11 So we could go "pepperoni" and then we separate each item with a comma.
• 01:16 So "pepperoni", "hamburger", "cheese", "mushroom", whatever.
• 01:23 That's an array, very simple.
• 01:25 So you can see I've got all this on one line, and
• 01:28 in fact you can put this on multiple lines, and that's sort of the convention.
• 01:32 Just because it makes it much easier to read.
• 01:34 This is a very small array, if you have a huge array with hundreds of things in it,
• 01:38 or something you wanna put it on separate lines,
• 01:40 just because it's gonna be easier to read.
• 01:42 So, we can call out things from our array, and we can and do things with them,
• 01:45 just like when we output variables to the screen we can do the same thing.
• 01:48 And we do that by referencing the index number of each item.
• 01:52 Each item in an array has its own index number.
• 01:55 And the numbers start at zero.
• 01:57 This is very important.
• 01:58 This screws up a lot of people.
• 01:59 So "Pepperoni," this is the zeroth item.
• 02:02 Right, it's not the first item, it's 0.
• 02:04 Hamburger is number 1, cheese is number 2, mushroom is number 3.
• 02:08 So there're 4 items in here, but it only goes up to 3 in index numbers.
• 02:13 That confused a lot of people.
• 02:14 Even to this day I'll forget every once in a while, and I'll wanna use pepperoni and
• 02:19 I'll call for variable index number one, and it'll be hamburger, and
• 02:22 I'll be like, yeah, I forgot, it's zero.
• 02:24 Try and keep that in mind.
• 02:25 So, to access an array item, all we have to do is just call our array,
• 02:31 do this, and boom, 0. That's it.
• 02:33 So if we wanted to go document.write, just like we have in the past for everything.
• 02:40 So we're calling out our array we wanna output the zeroeth item.
• 02:45 That's pepperoni.
• 02:46 If we wanna output the third item, that's mushroom.
• 02:50 We can also reference the entire array by not giving it an index number,
• 02:54 just calling it pizza.
• 02:55 If we do that, we're gonna get everything output separated by a comma.
• 03:00 Now we an loop through these and pull out each item automatically.
• 03:03 We're gonna talk about loops later.
• 03:05 And when we do, we'll look at arrays and loops and you'll see how to do that.
• 03:08 So you can put all kinds of things in arrays.
• 03:10 We've got strings here.
• 03:11 You can also put, we can put numbers.
• 03:14 That works just as well.
• 03:15 We can put other arrays in an array,
• 03:18 that will blow your mind later when we start to do that.
• 03:20 We can do math with arrays, so 41 and 2.
• 03:23 Now if we come down here and call pizza, let's see this is 0, 1,
• 03:28 2, 3, this is the 4th and the 5th item.
• 03:31 So if we go 4 + pizza 5,
• 03:39 Typo, 04 + 05.
• 03:42 That's gonna be 43.
• 03:43 So we can do addition,
• 03:44 we can do anything we want with an array that we can do with a variable, basically.
• 03:48 We can ask it what the length is,
• 03:50 how many items are in there by calling length, pizza.length.
• 03:55 And we can see there are six items in our array.
• 03:58 We can do sort which is kinda fun.
• 04:01 So we got pepperoni, hamburger, cheese.
• 04:04 If we sort them, it does it, oops, actually we need to sort and
• 04:08 then two little parenthesis.
• 04:10 Now it puts it in alphabetical order, now it's cheese, hamburger, mushrooms and
• 04:15 starts with 2 and 41 'cause 2 is smaller than 41 so that's automatically sorting for us.
• 04:20 We can add things to our array.
• 04:22 We can go pizza.push to push something in.
• 04:27 And then we can go, say, "onion", right.
• 04:30 Now, if we call our array,
• 04:31 we can see "onion" has been added to it automatically, programmatically.
• 04:37 So, those are arrays, they're really fun and
• 04:39 in the next video we'll talk about objects.

Lesson notes are only available for subscribers.