Functions

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Functions are blocks of code that can be named and reused.

Here’s how to declare a function:

EXAMPLE

function addTwoNumbers(x, y) {
       return x + y;
}

There’s a lot going on in the example above, so let’s look at each part individually.

function is the keyword that starts declaring a function.
addTwoNumbers is the function’s name, which is customizable — just like variable names.
(x, y) are parameters, variable names for the inputs a function will accept.
return is the keyword that exits the function and shares an optional value outside.

Using functions

Once a function is defined, you can use it by referencing its name with parentheses () right after.

Note that a function doesn’t have to have parameters.

EXAMPLE

function greetThePlanet() {
       return "Hello world!";
}
​
greetThePlanet();

OUTPUT

"Hello world!"

If a function does have parameters, you’ll need to provide values inside the parentheses when using the function.

EXAMPLE

function square(number) {
       return number * number;
}
​
square(16);

OUTPUT

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Next: Conditionals