What is JavaScript?

JavaScript is a scripting language that enables you to create dynamically control multimedia, animate images, pretty much everything else.
JavaScript is the world's most popular programming language.
JavaScript is the programming language of the Web.
JavaScript is easy to learn.

Why you should study JavaScript?

JavaScript is one of the 3 languages all web developers must learn
HTML to define the content of web pages
CSS to specify the layout of web pages
JavaScript to program the behavior of web pages

JavaScript Display Possibilities

Writing into an HTML element, using innerHTML.
Writing into the HTML output using document.write()
Writing into an alert box, using window.alert().
Writing into the browser console, using console.log().

JavaScript Variables

4 Ways to Declare a JavaScript Variable:

Using var
Using let
Using const
Using nothing

What are Variables?

Variables are containers for storing data (storing data values), In this example, x, y, and z, are variables, declared with the var keyword:

var x = 5;
var y = 6;
var z = x + y;
console.log(z);

Output: 11

x stores the value 5
y stores the value 6
z stores the value 11

JavaScript Arithmetic Operators

Arithmetic operators perform arithmetic on numbers (literals or variables).

#	Operators	Description
1	+	Addition
2	-	Subtraction
3	*	Multiplication
4	/	Division
5	++	Increment
6	--	Decrement

JavaScript Data Types

JavaScript variables can hold different data types: numbers, strings, objects and more:

let length = 16; // Number
let lastName = "Johnson"; // String
let x = {firstName:"John", lastName:"Doe"}; // Object

JavaScript variables can hold different data types: numbers, strings, objects and more:

In programming, data types is an important concept.
To be able to operate on variables, it is important to know something about the type.
Without data types, a computer cannot safely solve this:

JavaScript Objects

In real life, a car is an object
A car has properties like weight and color, and methods like start and stop
All cars have the same properties, but the property values differ from car to car.
All cars have the same methods, but the methods are performed at different times.

Examples for objects:

Example 1:

const car = {type:"Fiat", model:"500", color:"white"}; //This is an Object
console.log("The car type is " + car.type + "it's model is " + car.model + " and it's color is " + car.color)

Output:

The car type is Fiat it's model is 500 and it's color is white

Example 2:

const person = { firstName: "John", lastName: "Doe", age: 50, eyeColor: "blue" };
console.log(person.firstName + " is " + person.age + " years old and he's eye color is " + person.eyeColor)

Output:

John is 50 years old and he's eye color is blue

JavaScript Arrays

An array is a special variable, which can hold more than one value:

const cars = ["Saab", "Volvo", "BMW"];

Why we use Arrays?

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this

let car1 = "Saab";
let car2 = "Volvo";
let car3 = "BMW";

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?, The solution is an array! An array can hold many values under a single name, and you can access the values by referring to an index number.

Creating an Array

Using an array literal is the easiest way to create a JavaScript Array

Syntax:

const array_name = [item1, item2, ...]; //It is a common practice to declare arrays with the const keyword.

Example 1:

const cars = ["Saab", "Volvo", "BMW"];
console.log(cars);

Output:

[ 'Saab', 'Volvo', 'BMW' ]

Note:

The first element of the Array is always considered as 0

Example 2:

const cars = ["Saab", "Volvo", "BMW"];
console.log(cars[0]);
console.log(cars[1]);
console.log(cars[2]);

Output:

Saab
Volvo
BMW

You can also create an array, and then provide the elements:

const cars = [];
cars[0]= "Saab";
cars[1]= "Volvo";
cars[2]= "BMW";
console.log(cars);

Output:

[ 'Saab', 'Volvo', 'BMW' ]

More codes are coming