Javascript — Introduction
Some basics things to start with Javascript
Introduction to Javascript:
Javascript (“JS” for short) is a scripting language, commonly used to create interactive effects within web browsers. It was originally developed by Netscape as a means to add dynamic and interactive elements to websites. JS is used on both the client-side and the server-side to make our web pages effective and interactive. Where HTML and CSS are the structure and style of a web page, then Javascript is the logic that creates a dynamic and interactive experience for the user.
Javascript is basically a very versatile and beginner-friendly language. With more practice and experience, you will soon be able to create games, animated 2D and 3D graphics, comprehensive database-driven apps, and much more!
— You can add Javascript to HTML by following methods:
- Javascript in <head>
- Javascript in <body>
- External Javascript
JS bin compiler is best for online practice. Follow the below link and start practicing Javascript!!
→ Javascript in <head>:
In this type, Javascript is added in the head of the HTML file.
The function moreInfo() is called when a button is clicked.
Output before clicking the More Info button:
Output after clicking More Info Button: The selected paragraph is added to the introduction page after using Javascript.
→ Javascript in <body>:
In this type, Javascript is added in the body of the HTML file.
Output before clicking the More Info button:
Output after clicking the More Info button:
→ External Javascript:
In this type, we create an external javascript file (.js extension ) and link it with the HTML document in the <head> using the following line of code. In the src attribute, we will write our .js file name.
<script src=””></script>
Output before clicking the More Info button:
Output after clicking the More Info button:
You can find the code in below link:
Installing Nodejs:
Firstly, install nodejs in your system by using the below link.
https://nodejs.org/en/download/
In Javascript, the console.log() function is used to print any kind of defined variables or message that needs to be displayed to the user.
Variables — A variable is a container for a value, that we might use in a sentence or in the calculation. We define variables by using 3 keywords
- var → var keyword was the only way to declare a JavaScript variable, before 2015.
- let → let keyword be used to define variables with restricted scope.
- const → const keyword define variables that cannot be reassigned.
Datatypes — Javascript mainly has 2 datatypes
- Primitive datatypes → number, string, boolean
- Non-primitive datatypes → object, array, function
Number: Number is a primitive datatype. In Javascript, every number whether it’s an integer or float is considered a number datatype. The typeof function shows the datatype of the variable.
String: String is primitive datatype. It is a set of characters that can also contain spaces and numbers. In Javascript, we can initialize string in 3 ways
- Single quoted string → we use single quotation marks for string initialization.
- Double quoted string → we use double quotation marks for string initialization.
- Template Literals → Template literals are enclosed by the backtick (` `). These are indicated by the dollar sign and curly braces (
${expression}).
Boolean: It is a primitive datatype. Boolean datatype is a type that has a true or a false value.
Object: An object is a collection of properties, and a property is an association between a name (or key) and a value. A property’s value can be a variable or function known as methods. Curly brackets {} are used for containing object items.
Array: Array is basically a container that contains multiple items, items can be of the same datatype or different datatype. In Javascript, we can list different datatype variables into one array. An array is a non-primitive datatype and any non-primitive datatype is an object. Square brackets [] are used for containing array items.
You can find the practice.js code from the below link:
