JavaScript Variable in Hinglish: var, let, const Ka Easy Explanation with Examples

Namaskar Dosto!

aaj hum is article me jaanenge JavaScript Variables ke baare me — jaise ki var, let, const (Variables) kya hote hain, inke differences kya hain, variable scope kya hota hai, hoisting ka matlab kya hai, aur beginners kaunse common mistakes karte hain. Saath hi FAQs, naming tips, aur best practices bhi cover karenge — sab kuch simple Hinglish me, practical examples ke saath.

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JavaScript Variables Kya Hote Hain? (With Simple Example)

Jaise aap apna favourite chocolate ek box me rakhte ho, waise hi JavaScript me koi bhi value ko hum ek variable ke box me store karte hain.

let chocolate = "Dairy Milk";
console.log(chocolate); // Dairy Milk

Yaha chocolate ek variable hai, jisme “Dairy Milk” store kiya gaya hai. Jab bhi hume us value ki zarurat padti hai, hum is box (variable) ko use kar sakte hain.

Variables ka use hota hai data ko temporarily ya permanently store karne ke liye, jise hum program me baad me kabhi bhi access kar sakein.

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JavaScript Variables Kyu Important Hain?

Agar aapko kisi value (jaise naam, number, price) ko baar-baar use karna ho to har baar manually likhne ke bajaye, aap variable use kar sakte ho.

JavaScript Variables ke Fayde:

• Code readable aur manageable hota hai
• Same value ko baar-baar use kar sakte ho
• Value change karni ho to sirf ek jagah change karna padta hai

let userName = "Aditya";
console.log(userName);
console.log("Welcome, " + userName);

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JavaScript Me Variable Kaise Banate Hain?

JavaScript me 3 tarike se variable banaye ja sakte hain:

var name = "Aditya"; // Purana method
let age = 21;         // Modern method
const PI = 3.14;      // Jab value fix ho

Explanation:

• var: Old way, ab avoid karna chahiye
• let: Jab value update ho sakti hai
• const: Jab value fix ho aur kabhi nahi badlegi

MDN Docs – Declaring Variables

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var vs let vs const – Comparison Table

Hoisting ka matlab hai: variable ko declare karne se pehle access karna. var me yeh allow hai but value undefined hoti hai.

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Modern JavaScript Me Kaunsa Use Kare?

Aaj ke modern JavaScript standards ke hisab se:

• let ➝ Jab value update hone wali ho
• const ➝ Jab value fix ho
• var ➝ Avoid karo, kyunki yeh unpredictable behavior create karta hai

const appName = "Programming Sikho";
let visitorCount = 0;

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JavaScript Variable Scope Explained

Scope ka matlab hota hai ki koi variable kis area me accessible hai.

Types of Scope:

1. Global Scope – Puri file me variable accessible hota hai
2. Function Scope – Variable sirf function ke andar accessible hota hai
3. Block Scope – Variable sirf {} ke andar accessible hota hai (like if, for, etc.)

let score = 10;
if (true) {
  let score = 20;
  console.log(score); // 20 (block scope)
}
console.log(score); // 10 (outer scope)

Read More – JavaScript Scope (W3Schools)

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Variable Naming Best Practices

Valid Names:

let firstName;
let userAge;
let totalMarks;

Invalid Names:

let 123name;
let user age;
let @value;
let let; // Reserved keyword

Naming Tips:

• camelCase use karo (studentName, totalMarks)
• Reserved words avoid karo (let, var, const use mat karo as variable names)
• Naam meaningful aur clear hona chahiye

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JavaScript Variable Hoisting Samjho

var Hoisting Example:

console.log(a); // undefined
var a = 10;

var hoist ho jata hai lekin uski value undefined hoti hai jab tak assign na karo.

let/const Hoisting Example:

console.log(b); // ReferenceError
let b = 20;

let aur const hoist nahi hote. Agar unhe pehle access karoge to error milega.

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Common Mistakes with Variables (Beginners Beware!)

• const variable me new value assign karna
• Variable declare kiye bina use karna
• Spelling mistakes (e.g., usrName instead of userName)
• var ka overuse karna
• Scope ke concept ko ignore karna

const pi = 3.14;
pi = 3.1416; // Error: Assignment to constant variable.

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Real-Life Example: Form Input Store Karna

let userName = document.getElementById("nameInput").value;
console.log("User name is: " + userName);

Form input me se value leke variable me store karna ek common use-case hai.

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FAQs – JavaScript Variable Related Sawal

Q. var aur let me kya difference hai?
A. var function scoped hota hai, let block scoped hota hai.

Q. const me value update kyu nahi hoti?
A. const ka matlab hi hai constant — sirf ek baar assign kiya ja sakta hai.

Q. Kya variable declare kiye bina use kar sakte hain?
A. Nahi, pehle declare karna zaroori hai, warna error aayega.

Q. Kya ek variable ke andar function bhi store kar sakte hain?
A. Haan! JavaScript me function bhi variable me store kiya ja sakta hai.

const greet = function() {
  console.log("Hello!");
};

greet(); // Hello!

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Conclusion:

Ab aapne seekha:

• JavaScript variables kya hote hain
• var, let, const me kya farak hai
• Scope aur hoisting ka concept
• Naming best practices kya hain
• Common beginner mistakes kya hoti hain
• Real-world me variable kaise use hote hain

Agar aap in concepts ko clearly samajh ke practice karte ho, to JavaScript ki foundation bahut strong ho jaayegi.

Aapko ye article helpful laga ho to comment zaroor karna, aur apne doston ke saath share bhi karna.

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Next Article

JavaScript Kya Hai? Beginners ke Liye Complete Hinglish Guide

Written by: Aditya (Programming Sikho)