All language subtitles for 016 Revisiting Control Structures_en

So enough for hobbies

and objects for now, let's explore control structures.

I already mentioned the if keyword

which is used to create so-called if statements before.

The idea here is that you compare values, for example,

and you then execute the code inside of the if statement

only if this condition here is met.

Now the if statement also allows you to add a else statement

to define the code that should be executed

if this condition is not met.

And also else if statements if you want check

for more conditions if the first condition wasn't met.

And you can add as many else if statements here as you want,

but only one else branch.

Now of course, checking for hard-coded values like this

makes absolutely no sense.

This will always be true, for example.

Instead, typically, of course, you'll use if statements

to check content you don't know in advance.

For example, here I could get some dummy password

by using the built-in prompt function.

This is a function provided by the browser

which will prompt the user for input.

You see here I get this overlay that opens up.

Here I could type your password,

and now I would get this overlay

which asks me for a password.

Now here I'm getting this overlay

whenever I type a couple of characters in my code here,

and since this is a bit annoying,

I'll indeed go to the preferences here

and then the CodeSandbox settings

and set the preview settings to disable preview on edit

so that it will not automatically re-execute the code

after I typed a couple of characters.

So with that, I'm now fetching this password,

and I could now check if the password is equal

using the triple equals

and operator to hello, let's say, written like this.

And if that's the case, I'll console log, hello works,

else, if this condition here should not be met,

if the password entered by the user is not hello,

written like this,

I could check if the password is maybe equal to hello,

starting with a lowercase L,

in which case, here, I could console log hello works.

But also, if that's also not the case,

I might want to execute this fallback code here

where I say access not granted.

With this, now if I save this,

the code does get executed again,

but I'll still cancel this

and manually refresh to clear the console.

And now if I enter hello with a capital L,

and press okay in my console, I'll see hello works,

because since I entered hello, written like this,

this condition here was met and this code here was executed.

On the other hand, this code and this code was not executed.

That's why the if statement is called a control structure

because it controls which code gets executed.

If I reload this

and I enter anything else like this here,

and I press okay, I get access not granted,

because of course I didn't never enter hello

written like this nor written like this.

Therefore, this code got executed.

So that's the if statement.

Another crucial control structure

you should know about is the for loop.

Now JavaScript knows different types of for loops,

one very important kind of for loop

we'll also see in this course is the for loop

where we loop through an array.

For that, I'll again create my hobbies dummy array here

with sports and cooking, let's say,

and now if I want to execute some code,

for every entry in this array,

I could create a for loop where I create a constant

that will be recreated for every iteration of that for loop,

because for loops are about executing

the same piece of code multiple times, as you will see.

And I could name this constant, hobby,

because now with the special of keyword,

I tell JavaScript that it should create a new constant

for every item in this array,

and it should execute the code

between these curly braces as often as needed

to go through all these elements in this array,

so for this array, two times.

So if I then console log hobby here, for example,

this code, this console log code will get executed twice

because I have two elements in this array.

The first time for hobby being equal to sports,

the second time for hobby being equal to cooking.

If I save this

and I reload here, enter anything here

and open the console, I see sports

and cooking being output here

because of this line of code being executed multiple times.

So this for of loop is also a kind of loop

you should be aware of

because we'll also see this in this course.