Javascript Variables

noreply@example.com (AG Sayyed) — Mon, 24 Mar 2025 03:28:07 +0000

This document explains JavaScript variables, their declaration, initialization, and scope, as well as control statements like conditional statements, switch statements, and loops. It highlights how these features enable dynamic program flow and efficient data handling in JavaScript.

JavaScript Variables

Declaration and Initialization

Variables are declared using the var keyword followed by the variable name, e.g., var age.
Variables can be initialized during declaration, e.g., var age = 54, or assigned a value later.
JavaScript is loosely typed, so variables take their data type from the assigned value and can change type during execution.
Uninitialized variables have a value of undefined.

Rules for Variable Names

Must start with a letter, underscore (_), or dollar sign ($).
Subsequent characters can include letters, digits (0-9), underscores, or dollar signs.
Variable names are case-sensitive.

Scope of Variables

Local Scope: Variables declared within a function are accessible only inside that function.
Global Scope: Variables declared outside a function or without the var keyword are accessible throughout the program.

Example: Variable Declaration and Control Statements

Variable Declaration

1var name = 'John'
2var age = 30
3console.log(name + ' is ' + age + ' years old.')

If Statement

1if (age > 18) {
2 console.log('Adult')
3} else {
4 console.log('Minor')
5}

For Loop

1for (var i = 0; i < 5; i++) {
2 console.log('Iteration ' + i)
3}

Conclusion

JavaScript variables allow dynamic data handling with flexible typing and scoping rules.

Javascript-Variables on Ghafoor's Personal Blog