For Loops

Quick reference

• 00:04 We've talked about If statements and
• 00:06 switch now it's time to move into the loops, and loops are great.
• 00:08 They're another one of those fundamental programming concepts that all programming
• 00:12 languages have, and you'll use loops all the time for a bunch of different things.
• 00:16 So, what exactly is a loop?
• 00:18 Well basically a loop is just what it sounds like,
• 00:20 it allows us to loop through things and do them over and over programmatically.
• 00:24 Now there're several different types of loops and
• 00:27 they all do things slightly differently and you'll learn as you get more
• 00:30 experience which type of loop to use in different circumstances.
• 00:33 In this video we're gonna look at For loops.
• 00:36 And For loops loop through a block of code a number of times and
• 00:40 they basically have this general format.
• 00:44 I can look at this and its for that's our For loop, and then we have statement one,
• 00:48 statement two, and statement three, separated by semicolons, and
• 00:52 I'll talk about these in just a minute.
• 00:54 And then inside of here, here's the code that we're gonna loop through.
• 00:59 So what are these weird statement things?
• 01:01 What's going on here?
• 01:02 So statement one is executed before the loop starts right away, okay.
• 01:07 Statement 2, let's us defined a condition, sort of like an if statement,
• 01:10 remember there's a condition.
• 01:12 And statement 3, gets done after we have looped through one time.
• 01:16 So, every time we looped through, after we loop we'll do statement 3.
• 01:19 So, statement 1, you start, statement 2 is your condition and
• 01:23 statement 3 is whatever you wanna do after you have looped.
• 01:26 So it sounds a little bit confusing but let's just go ahead and build one and
• 01:29 we'll see that it's not really that bad at all.
• 01:31 So I'm just gonna delete this and let's go for, call it a For loop,
• 01:37 and let's create a variable i = 1; that's our statement one.
• 01:42 And for our condition, let's say i < 10.
• 01:46 So any time i is less than 10, we wanna keep looping.
• 01:50 And statement three at the end.
• 01:52 What we wanna do is, let's increment i one time.
• 01:55 Remember our incremental?
• 01:57 So then, we just open and close our brackets and
• 02:01 now anything here in the middle.
• 02:03 This is what's we're gonna loop through.
• 02:06 So let's go document.wright, and let's say what?
• 02:11 Let's just print out the number to the screen.
• 02:14 And let's give it a line break so that it's not all on one line.
• 02:20 Okay so, we start out i as 1.
• 02:22 We check to see if it's less than 10.
• 02:24 And then we increment and we write it out to the screen.
• 02:26 So let's go ahead and click reload.
• 02:28 And we can see 1, 2, 3, 4, 5, 6, 7, 8, 9.
• 02:30 Why did it stop at 9?
• 02:32 Because when we get to 10, after 9, it increments with our statement three.
• 02:36 And it becomes 10 and then it starts over and it says is i < 10.
• 02:40 Is 10 < 10?
• 02:44 No, 10 is not less than 10.
• 02:45 So in that case the whole thing stops.
• 02:48 So this keeps going as long as this is true.
• 02:51 So we've got this less than, we can use our conditional statements greater than,
• 02:56 greater than equal to, equal whatever we want, we can use there, so
• 03:00 that's pretty much it.
• 03:01 And a For loop is kind of the more complicated loop because we have all these
• 03:04 different moving parts, there's all this stuff going on,
• 03:07 it seems a little bit complicated.
• 03:08 And like I said you'll use loops all the time for all kinds of different things.
• 03:12 They're just a fundamental programming building block one of those things.
• 03:16 So that's For loop.
• 03:17 In the next video we'll look at While loop.

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