All language subtitles for 8- Types of Functions

Now there is a

cleaner way to write this code on line 3, all this concatenations

are kind of ugly, they're getting in the way, later in the course I will show you

how to use template literals to clean up this code. For now,

don't worry about it, let's look at another example of a function.

This function we have here is performing a task. So,

Performing a task. This task is to display something on the

console. But sometimes our functions might calculate something,

so, here is an example of a function that calculates

a value. So again, function, let's call

this function square, this function should take a parameter, let's call

that number, now we need to calculate the square

of that number, that is number times number.

Just basic math. Right? Now we need to return this value

to whoever is calling this function. For that we use

the return keyword. That's another reserve keyword

so we cannot have a variable called return, okay? Now instead of

calling the greet function, let's call the square function. So,

square, we pass 2, now this returns a value

so we can use that value to initialize a variable.

For example, you can declare another

variable called number, and set it to a square of 2.

And then we can display that on the console.

Save the changes, so we get 4. Now,

in this particular example, we don't necessarily have to declare a separate

variable if all we want to do is display the square of 2

on the console. We can exclude this variable declaration,

and simply pass square of 2,

to console.log.

So, when the JavaScript engine executes

this code, first it's going to call this function, it will get a value

and then pass that value to console.log.

Save the changes and look we still get 4.

Now, I have a question for you. How many function calls do you think we

have in this code? We have 2 function calls.

Square of 2, is one function call, let me

delete this temporarily, but console.log is also

another function call, right? Because here we have parenthesis,

so, we're calling the log function, which is defined somewhere,

and passing an argument, we can pass a simple string,

like Hello, or we can pass an expression, that expression can be

a call to another function, like square of 2.

Okay? So this is the basics of functions. Again, later,

in the course we have a comprehensive section about functions, for now, all I want

you to take away, is that a function is a set of statements

that either performs a task, or calculates

and returns a value. A real world application is essentially

a collection of hundreds or thousands of functions working together

to provide the functionality of that application.