Understanding Functions Better

Functions are very important and useful in any programming language, as they make the code reusable.

A function is a block of code which will be executed only if it is called.
If you have a few lines of code that needs to be used several times, you can create a function and then call the function wherever you want to do the task you want.

Briefly, why Functions?

You can reuse code: Define the code once, and use it many times.
You can use the same code many times with different inputs, to produce different results.

How to Create a Function in JavaScript

Use the keyword function followed by the name of the function.
After the function name, open and close parentheses.
After parentheses, open and close curly braces.
Within curly braces, write your lines of code.

Example:

Function with Arguments

You can create functions with arguments as well. Arguments should be specified within parentheses

Try the example below in your code editor:
Notice how we are calling the make_double function and give it an input number, a parameter.

JavaScript Return Value

You can also create JS functions that return values. Inside the function, you need to use the keyword return followed by the value to be returned.

Try the example below in your code editor:
Notice how we are calling the future_age function and it returns the number.

Functions in JS