The for loop is the loop structure that I most frequently use. It's the one I prefer. And it's probably the most frequently used in most JavaScript code. Now, before I introduce the syntax of the for loop, let's take a look at the while while loop example that we just completed. So I'm going to jump to sublime. Now notice there's a couple of things in this while loop that we do.

We have a counter that we initialize and set to zero. We then in a condition, check that counter, and then we increment that counter. So there's three things we do with this counter as a part of this while loop. Well, the for loop allows us to do all three of those things within the loop structure. So let's take a look at that syntax. So we first have the the keyword for, that's a reserved word.

And then inside of parentheses, we do three things, we do those three things I talked about, we have the initialize expression, where we usually initialize a variable, we then have a condition where we check that variable for true or false. Then we modify the expression. And usually that means changing that variable in some way. So with the example of the while loop I gave, we would initialize count, we would check count and then we would increment count. Then of course, we have the block to execute and that block continues to execute as long as the condition part of the for loop evaluates to true. Once it evaluates to false, then exit exits out of the loop.

All right, let's do a couple of examples. Jumping back to sublime. I'm going to remove everything we did in the previous example. However, I do want to keep this sentence I'm going to use it in our second example. This first example will be a pretty simple one. Let's say we simply wanted to print out one through 10. on separate lines in the console, something very simple like that.

So let's see how we would do that. With a for loop we first indicate that it is a four loop using the keyword four. And then we have our parentheses. And then the curly braces to define the code block that we want to execute. So inside of the parentheses, we first have an initialize expression. So we're going to initialize a variable i is equal to one and then we put a semi colon So the three parts in the for loop are separated by a semicolon.

The second part is the condition, we want to print out the numbers one through 10. So we want to do this loop, while i less than or equal to 10 i less than or equal to 10, then another semi colon. Now this is where we change the expression. So in this case, we're going to increment the variable. We do that with the increment operator, like that. Now, the only statement we need to put in is console dot log.

Hi. And that will print from one to 10. Let's go ahead and give that a try. copy the file path, jump out. paste that into the browser, open the console. And as you You can see we have printed out the numbers one through 10.

Okay, so that worked great for us. Let's do another example a bit more complex example. This time, we're going to use the same sentence that we use for the while loop. But this time, what I'd like to do is print out the sentence in reverse order. So we reverse the all the characters in the sentence, so that we print it backwards. So to do that, I'm going to declare a second variable where we will store the backwards sentence.

So I'm just going to call that backwards. I'm going to set it equal to double quotes, quotes without anything in it an empty string because I know this is going to be a string. And so I declare it and set the initial value as a string. All right, now let's do our loop for var I equal. Now what are we going to start at? Well, if we want to get this sentence starting at the end of it, and then move this direction, we need to set it to the this character position.

So how would we determine that character position? Well remember the position start with zero. All right? So we could use the length property of the string object wrapper, subtract one from it, and that would give us that character position. Because the length is the total number of characters, the position starts with zero. And so that's why we would have to subtract one.

So let's do that. Let's do sentence dot length. minus one. Okay. That's that will initialize. I now We want to run this loop until I or while i is greater than or equal to zero.

So once it becomes less than zero we want it to exit out of the loop. And finally, we want to this time decrement I because we're going from the highest to the lowest number All right, let's put our curly braces in this will be our block of code. What we want to do now is we want to set backwards equal to this new string we're creating. And so the way we can do that is we do backward equal to backward what we already have in there. Plus sentence dot character at I know let me explain this. So the first time we go through the loop backward is going to be nothing so we will concatenate nothing to exclamation point.

Backward becomes exclamation point, the next time through the loop, we can cap, concatenate x, exclamation point to E. So backward now becomes exclamation point E. Next time through the loop, we concatenate C to all of that. So you can see that eventually when we finish, we will have the sentence in reverse order. So once we exit out of the loop, we can just do console dot log backward and that with a semi colon. Let's go ahead and save this. And let's see how it works. So we'll come out to the browser refresh that.

Sure enough, it printed the sentence in reverse order. All right, in the next movie, we'll do one more for loop example.