functions.js

/*
 * Functions always return a value. In JavaScript, if no return value is specified, the function will return undefined.
 * Functions are objects. In JavaScript, anything that is not a primitive type ( undefined, null,boolean, number, or string) is an object. 
 * When using function Declarations, the function definition is hoisted, thus allowing the function to be used before it is defined.
 * A Function Expressions defines a named or anonymous function.  Function Expressions are not hoisted, and therefore cannot be used before they are defined. Different from Function Declaration.
 * Arrow Function Expression, they do not create their own "this" value. Sometimes can be usefull to avoid bind with the event handlers.
 * Values can be passed into functions and used within the function. The name of the value is called a parameter. The actual value itself is called an argument.
 */

/***********************************************************FUNCTION DECLARATIONS EXAMPLE************************************************************/

//definition is hoisted and awailable
console.log(square(5));

function square(n) {

    return n * n;
}
/***************************************************************************************************************************************************/

/***********************************************************FUNCTION EXPRESSION EXAMPLE************************************************************/

//function is not hoisted, so cannot be used before definition, this line will throw error "sum is not defined"

console.log(sum(5, 2));

let sum = function(a, b) {

        return a + b;
    }
    /***************************************************************************************************************************************************/

/********************************************************ARROW FUNCTION EXPRESSIONS EXAMPLE**********************************************************/

//Definition
let showMessage = () => {
    console.log('Hello');
}

//Execution
showMessage();

//Self executed arrow function expression
(() => {
    console.log('Hello Self Executed');
})()
/***************************************************************************************************************************************************/