Ayan Choudhury
Founder & CEO - TheoreX | Startup Enthusiast | Open Source Enthusiast | Wikimedian | Mozillian
Small
Light-Weight language
Contains standard library of objects like 'Array', 'Date', 'Math' etc.
Extends the core language by supplying objects to control a browser and its Document Object Model (DOM)
Client-side extensions allow an application to place elements on an HTML form and respond to user events such as mouse clicks, form input, and page navigation
extends the core language by supplying objects relevant to running JavaScript on a server
It allows an application to communicate with a database, provide continuity of information from one invocation to another of the application, or perform file manipulations on a server
Fundamentally they are different
The Differences...
Java is completely a programming language, whereas JavaScript is a coded program that can be introduced into HTML pages
The Differences...
Java is an Object Oriented programming language or rather structured language like C or C++ whereas JavaScript is a client side scripting language and it is said to be unstructured programming
Getting Started
Basics...
Borrows most of its syntax from Java & also influenced by AWK, Perl & Python
Basics...
It is Case Sensitive & Uses Unicode character set.
JavaScript Output
JavaScript can display data in different ways:
1. alert box - window.alert()
2. HTML output - document.write()
3. HTML Element - innerHTML
4. Browser Console - console.log()
window.alert()
document.write()
innerHTML
console.log()
JavaScript Syntax
A set of rules how JavaScript Programs are constructed. A computer program is a list of instructions to be executed by the programmer. In a programming language these are called statements. JavaScript statements are separated by semicolon.
JavaScript Statements
These are composed of 5 things:
1. Values / Variables
2. Operators
3. Expressions
4. Keywords &
5. Comments
JavaScript Declarations
There are 3 types of Declarations
1. var - declares a variable
2. let - declares a block scope local variable
3. const - declares a read-only named constant
Variables
A JavaScript identifier must start with a letter, underscore (_), or dollar sign ($); subsequent characters can also be digits (0-9). Because JavaScript is case sensitive, letters include the characters "A" through "Z" (uppercase) and the characters "a" through "z" (lowercase).
Declaring Variables...
Keyword -> 'var'
var x = 12
Can be used to declare both Global and Local variables
x = 12
This simply declares a Global variable, can't be used locally
Declaring Literals
Literals are the fixed values in a JavaScript Program
Numbers
Strings
Expressions
JavaScript Operators
Two types of JavaScript Operators are there...
1. Assignment Operator
2. Arithmetic Operator
Assignment Operator (=)
Arithmetic Operators (+-*/)
JavaScript Keywords
JavaScript is Case Sensitive
The variable 'lastName' and 'lastname' are two different variables as all the JavaScript identifiers are Case Sensitive
JavaScript Statements
The statement tells that the browser to write "Hello World" inside an HTML element with id="demo"
Semicolons ;
Semicolons separates JavaScript Statements
When separated by Semicolon multiple statements in a single line is allowed
JavaScript White Spaces
JavaScript ignores multiple spaces. You can white spaces to make it more readable.
JavaScript Line-Length & Line-Break
For best readability, programmers often like to avoid code lines longer than 80 characters.
If a JavaScript statement doesn't fit in one line, the best place to break it is, after an operator
JavaScript Code Blocks
JavaScript statement can be grouped together into code blocks (inside curly bracket {...})
Purpose of code blocks is to define statements to be executed together
JavaScript Keywords
1. break - terminates a switch loop
2. continue - jumps out of a loop and starts at the loop
3. debugger - stops the execution of JavaScript and calls the debugging function (if available)
4. do...while - executes a block of statements & repeats when the condition is true
5. for - marks a block of statements to be executed as long as the condition is true
Keywords...
6. function - declares a function
7. if...else - marks a block of statements to be executed depending upon a condition
8. return - exits a function
9. switch - marks a block of statements to be executes depending upon different cases
10. try...catch - implements error handling to block of statements
11. var - declares a variable
Keywords (contd...)
JavaScript Comments
Example...
JavaScript Data Types
JavaScript variables can hold number like 100 or string like "Hello World". Javascript can handle many types of data but among them the two most imp datatypes are number and string
Declaring JavaScript Variables
Example
Value = undefined
A variable declared without a value will be declared as a undefined variable
JavaScript Operators
+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus
++ Increment
-- Decrement
JavaScript Assignment Operators
Operator Example Same As
= x = y x = y
+ = x + = y x = x + y
- = x - = y x = x - y
* = x * = y x = x * y
/ = x / = y x = x / y
% = x % = y x = x % y
JavaScript String Operators
The + operator is used to concatenate strings
Adding Strings and Numbers
Adding two numbers will return a number but adding a number and a string will return a string
JavaScript Comparison & Logical Operators
Operator & Operands
Operands - The numbers in an arithmetic operation
Operator - The operation to be performed between to operands
By Ayan Choudhury
Founder & CEO - TheoreX | Startup Enthusiast | Open Source Enthusiast | Wikimedian | Mozillian