Variables in Javascript
A variable in JavaScript is like a container that stores data values. Just like a labeled box where you can put items to find them later, a variable holds information that can be used and updated throughout your code.
In JavaScript, variables are used to store and manipulate data. Think of variables as containers or "storage boxes" that hold information that can be referenced and used throughout a program. Variables make your code dynamic, allowing you to assign values that can be changed or reused.
Declaring Variables in JavaScript
JavaScript allows three primary ways to declare variables:
1. var - The original way to declare variables. However, var has some unique behavior (like hoisting and global scope issues), so it’s now less commonly used in modern JavaScript.
2. let - Introduced in ES6 (ECMAScript 2015), let allows you to declare variables with block scope, making it safer and more predictable than var.
3.const - Also introduced in ES6, const is used to declare variables with a constant (unchanging) value. Once assigned, its value cannot be reassigned.
// Using var
var age = 25;
// Using let
let name = "Alice";
// Using const
const birthYear = 1998;
Rules for Naming Variables:
When naming variables, JavaScript has specific rules:
1. Start with a Letter, Underscore, or Dollar Sign:
Variable names cannot start with a number.
They must begin with a letter (a-z or A-Z), an underscore (_), or a dollar sign ($).
2. Cannot Use Reserved Keywords:
JavaScript has certain keywords that are reserved, like if, else, function, and return. These cannot be used as variable names.
3. Case Sensitivity:
JavaScript is case-sensitive, so myVariable and MyVariable are two different variables.
4. Meaningful and Descriptive Names:
Always try to choose meaningful names that describe what the variable holds, making the code easier to read and understand.
5. Camel Case for Multi-Word Names:
In JavaScript, the standard naming convention for variables is camel case. This means the first word is lowercase, and each following word starts with an uppercase letter.
Examples of Valid and Invalid Variable Names:
