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Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examplesHello folks, I hope you are having a great day. Today, I am going to start this new tutorial series on JavaScript and here’s our 1st tutorial titled Introduction to JavaScript. This is a beginner level tutorial series, where we will start from very basics & will slowly move towards complex concepts. 

We can use any development Editor for running JavaScript and for this tutorial series, I will use Microsoft Visual Studio Code, which is free to use & you can download it from official site. You don’t need to be an expert programmer, in order to learn JavaScript, but you must have some basic knowledge of HTML & CSS. So, let’s get started with today’s lecture:

What is JavaScript – A Quick Definition

  • JavaScript ( initially named as LiveScript, officially named as ECMAScript ) is a client-side scripting language, developed by Brendan Eich in 1995 and is used to create interactive webpages and mostly used in game development.
  • Before JavaScript, webpages were dull and has no way to interact with the user, as we had only server side languages ( php, java etc. ) at that time and in order to get any action done, we have to send request to the server.
  • With JavaScript, now we can perform any complex task without refreshing the page, JavaScript works on client side that’s why there’s no need of page refreshing.
  • You must have noticed on your Facebook / Twitter profile that they update automatically, that’s because of JavaScript.
  • As JavaScript is a client side language so it can’t communicate directly with the server i.e. database or file system.
  • JavaScript is normally confused with Java, but they are two entirely different languages, Java is server side complex language while JavaScript is a simple scripting language.
How to Run JavaScript Code?
  • As I mentioned earlier, JavaScript is a client side scripting language, so we don’t need any compiler or editor for running JavaScript.
  • Instead, JavaScript is directly executed by the web Browsers, similar to HTML & CSS, which are also client side languages.
  • When a user makes an HTTP request, then browser reads the webpage and along with HTML,CSS etc. it also finds the JS scripts and executes them.
  • All modern browsers support JavaScript and you can enable / disable JavaScript in your browser’s settings.
  • Moreover, JavaScript works on almost all operating platforms i.e. Windows, Linux, Mac, Ubuntu etc.
  • So, in order to run JavaScript, you can use any Programming Environment / Editor i.e. Sublime, Notepad++, Visual Studio Code etc.




Uses of JavaScript

So, now let’s have a look at few uses / advantages of Javascript:

  1. Developing Mobile Applications & Games.
  2. Web Browser-based Games.
  3. Add interaction to websites.
  4. Back end web Development.
  5. Rich interface for Applications and web pages.

How to Include a JavaScript Code in HTML WebPage

  • As I have mentioned earlier, we don’t need any editor to run or execute JavaScript. Instead, web browsers execute the JS code on their own.
  • But question is, How web Browsers are going to recognize that its a JS code ??
  • And the answer is, the code placed between <script> </script> tags will be treated as a JavaScript Code.
  • There are two ways to include the JavaScript code in an HTML webpage, discussed as follows:
Embedding JavaScript Code directly in HTML Page
  • When we add JavaScript directly in <body> tag of our HTML page, it is termed as Embedded JavaScript.Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • In our HTML page, we can place JavaScript Code in the <script> </script> tags, as shown in the figure:
  • You can see in the figure that I have added a simple JavaScript Code:

<script> alert(“I am learning JavaScript”);    </script>

  • To run this code you have to add an extension. Go to the left side of visual studio and click on extension or press Ctrl + Shift + X buttons. 
  • Afterwards, Search “Open in browser” and install the first file. Look below in the image for more detail.Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • When your exertion is installed, now go back to your HTML file and press Alt + B. It will run your code. 
  • You will see something similar to below image, in your browser.Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • This is a simple JavaScript alert message, displaying our content.
Include External JavaScript File in HTML WebPage
  • If we add JavaScript Code directly in HTML page then it will make the code quite messy.
  • So, it’s always a best practice to create a separate file for JavaScript ( extension .js ) and then include this file in your webpage.
  • By convention, If your JavaScript code is more than 10 lines, then it’s better to add an external JavaScript file.
  • It also reduces the code repetition i.e. if you are using your JS code for multiple pages.
  • Let’s see now, how to add an external JavaScript file:

Steps to Follow:

  • Create a new file by pressing Ctrl + N and add alert(“Introduction to JavaScript”);” content in this file. Save it with the name “Test.js”. Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • As you can see on the right side in the figure.
  • Now go back to the “index.html” file and add the code as you can see in below figure: Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • When you will refresh the web browser then it will automatically reload a JS file through source code, as shown in below figure:

Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples

What Is The Best Way To Include JavaScript File in Html

  • You can add <script> tag in the <head> section of your HTML file, in the start of the <body> tag and also at the start or end of the body tag.
  • But I would advise you to add it at the end of the <body> tag. I will show you why it should be at the bottom of the body tag.
  • The HTML page always loads from top to bottom. And if your JS file will be in <head> tag or opening of the <body> tag. Therefore, it’s gonna run JavaScript first before loading any of the content in and it will leave a negative impact on your webpage. Let me show you now how it will drop a negative impression on your website.
  • Here is a basic example for you. As you can see in below image that I have added <script> tag at the start of <head> tag and add a new tag of <h1> for your understanding. Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples



  • Save these file and press ALT + B to execute this code. You will notice that as you see in the picture underneath that only <script> tag alert comes up first without loading the rest of page. Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • But once I click at ok then it has loaded the rest of the page now. As indicated in the image here. Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples

 

  • It leaves a bad impact on users because the page is loading step by step but not at once. Now I am gonna add <script> at the bottom of the <body> tag and as you can see in image down.Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples
  • Now save it go again to the browser and reload the page.  Instantly you can see the content and alert form at the same time. This is a perfect way of adding JS. Introduction to JavaScript with complete Guide, what is javascript, javascript tutorial with examples, javascript tutorial for programmers, learn javascript step by step, complete javascript tutorial with examples

I am sure you all already know HTML and CSS but you have attempted to learn JavaScript many times but failed for some reason and you drop it. But I am sure now you are going to stick with me since I am going to describe you step by step each code.
From the next lesson onward, I am going to tell you more in detail what is the Syntax of JavaScript and where to place JavaScript file. I hope you guys understand this lesson and I will see you in my next tutorial. Till then take care of yourself.

If YOU have any question regarding this post feel free to comment below and ask about it.  I will definitely reply to your query as soon as possible. 

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