Functions are very important when working with JavaScript. We will also use functions a lot in our examples.

The following code demonstrates the basic syntax of a function. It does not have arguments or the return statement:

function sayHello() { 
  console.log('Hello!'); 
} 

To call this code, we simply use the following call:

sayHello(); 

We can also pass arguments to a function. Arguments are variables with which a function is supposed to do something. The following code demonstrates how to use arguments with functions:

function output(text) { 
  console.log(text); 
} 

To use this function, we can use the following code:

output('Hello!'); 

You can use as many arguments as you like, as follows:

output('Hello!', 'Other text'); 

In this case, only the first argument is used by the function and the second one is ignored.

A function can also return a value, as follows:

function sum(num1, num2) { 
  return num1 + num2; 
} 

This function calculates the sum of two given numbers and returns its result. We can use it as follows:

var result = sum(1,2); 
output(result);