Functions are one of the fundamental building blocks in Javascript. A function is basically a set of statements that performs a task or calculates a value.

Example 1:

function greet() {

    console.log(‘Hello World’);

}

greet();

Example 2:

//Name is a parameter of the greet function

function greet(name) {

    console.log(‘Hello’ + name);

}

//John is an argument to greet function

greet(‘John’);  

greet(‘Mary’);

Example 3:

//Performing a task

function greet(name, lastName) {

    console.log(‘Hello ‘ + name + ‘ ‘ + lastName);

}

greet(‘John’, ‘Smith’);  

Example 4:

//Calculating a value

function square(number) {

    return number * number;

}

let number = square(2);

console.log(number);