JavaScript : A trending scripting language

JavaScript
“A simple way to get more.”
Abhay Dhupar
abhaydhupar123@gmail.com

What is JavaScript ?
• JavaScript is one of the most popular and widely used programming language in the world
right now.
• It’s growing faster than other programming languages and big companies like Netflix,
Walmart and Paypal build their entire applications around JavaScript.
•
• US offers 75000 dollars per annum to JavaScript developers on an average.
• You can work as a -
Front-end
Developer
Back-end
Developer
Full-stack
Developer

What can you do with JavaScript ?
• For a long time, JavaScript was only used in browsers to build interactive web pages.
• Some developers referred to JavaScript as a toy language, but those days are gone because
of huge community support and investments like large companies like facebook and google.
• These days you can build -
Web / Mobile
Apps
Command-line
Tools
Real-time
Networking
Apps
Games

Where does JavaScript code run ?
• JavaScript was originally designed to run only in browsers. So every browser has JavaScript
Engine that can run JavaScript code. In Chrome, this engine is v8.
• In 2009, a very clever engineer called Ryan Dahl took the open source JavaScript Engine in
Chrome and embedded it in a C++ program. He called that program Node.
• So Node is a C++ program which includes Google’s v8 JavaScript Engine. Now with this, we
can run our JavaScript code outside of a browser. So we can pass our JavaScript code to
node for execution. So with JavaScript, we can build the backend for our web and our
mobile applications.
• Browser and Node provide a runtime environment for our JavaScript code.

Let’s see JavaScript in action.

Editor and Other requirements
• In order to write JavaScript code, you’ll need a code edit a code editor
• Following are some of the commonly used -
VS Code Sublime Atom

Download Node
• Technically, you don’t need Node on your machine for learning JavaScript, as you can do in
browser as well.
• But it is good to have Node in your machine to install third party libraries.

JS through web browser
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<h1>Hello Abhay</h1>
<script>
console.log("Hello World") //Output(in your browser) inspect -> console
</script>
</body>
</html>

Separation of Concerns
• Now while we can easily write JavaScript code in between the script element. In a real-world
application, you have thousands or even million lines of code.
• We don't want to write all that code inline here we want to extract and separate our
JavaScript code from our HTML code.
• Let’s understand by a metaphor - Think of your house. In your bedroom, you have your bed
and your clothes.
• You don’t store your clothes in the kitchen. This is what we call separation of concerns.
• We have the same principle in programming, so we want to separate HTML which is all
about content from JavaScript which is all about behavior.

JS through Node
• Open your .js file location.
• Open up cmd or terminal at same location.
• Now write node file_name.js
• Use Integrated terminal in VS Code.

Variables
• We use variables to store data temporarily.
• Use var keyword to declare a variable.
• There are issues with var, we can also use let
• Ex - var my_name = 'Abhay';
console.log(my_name);
Rules
• It cannot be a reserved word.
• It cannot be start with a number.
• It cannot contain a space or hyphen (–). We can either use CamelNotation.
• It is case sensitive.

What type of value can we store ?

JavaScript : A Dynamic Language

Object
• Object is a real world entity.
• For example – instead of giving name, age of a person; we can create a person object.
• Ex -
let person = {
name: 'Abhay',
age: 30
};
// dot notation
person.name = 'John';
// Bracket notation
person['name'] = 'Mary';
console.log(person);

Arrays
• Array in JS is also a object.
• Sometimes in your application, you need to deal with list of objects.
• So to store that list of objects, we need arrays.
• Since JS is dynamic so size and data type in array can change in run time.
• Ex – list of product, list of students.
let array = ['Abhay','CSE']
array[2] = 1
console.log(array)
console.log(array.length)
console.log(typeof(array));

Functions
• Functions are one of the fundamental building blocks in JS.
• Functions are used to perform a task.
• function keyword is used to declare a function.
function greet(fname, lname) {
console.log('Hello '+ fname + ' ' + lname)
}
greet('Abhay','Dhupar');

JavaScript : A trending scripting language

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