JavaScript Syntax & Rules Kya Hote Hain?

1. JavaScript Syntax Kya Hai?

Har programming language ki tarah, JavaScript ke bhi apne niyam aur kanoon hote hain, jinhe syntax kaha jaata hai. Yeh syntax code likhne ka sahi format aur structure batata hai. Agar aap syntax follow nahi karte, toh JavaScript engine aapke code ko samajh nahi payega aur error dega.

// Yeh ek valid JavaScript statement hai
console.log("Hello, World!");

Yahan, console.log() ek predefined method hai jo console par output dikhata hai, aur "Hello, World!" ek string hai.

2. JavaScript Statements

JavaScript code statements se milkar banta hai. Har statement ek instruction ya command hota hai jo browser ko perform karna hota hai, jaise variable banana, value calculate karna, ya screen par kuch print karna.

Semicolons (;)

JavaScript me har statement ke end me semicolon (;) lagana ek acchi practice hai. Halaanki, JavaScript me Automatic Semicolon Insertion (ASI) hota hai, jo apne aap semicolon laga deta hai, lekin is par depend rehna errors ko janam de sakta hai.

let x = 10;
let y = 20;
let sum = x + y;
console.log(sum); // Output: 30

3. JavaScript Comments

Comments code ka woh hissa hote hain jise JavaScript engine ignore kar deta hai. Inka use code ko explain karne, notes likhne, ya code ko temporarily disable karne ke liye hota hai.

(A) Single-line Comments

Single-line comments double forward slashes (//) se shuru hote hain.

// Yeh ek single-line comment hai
let name = "Amit"; // Variable 'name' declare kiya gaya

(B) Multi-line Comments

Multi-line comments /* se shuru hote hain aur */ se end hote hain.

/* 
  Yeh ek multi-line comment hai.
  Iska use code ke bade sections
  ko explain karne ke liye hota hai.
*/
let age = 25;

Key Takeaways

• JavaScript ka code statements se bana hota hai, aur har statement ke end me semicolon (;) lagana best practice hai.
• Comments code ko readable banate hain. Single-line ke liye // aur multi-line ke liye /* ... */ use karein.
• JavaScript case-sensitive hai, yaani `myVariable` aur `MyVariable` do alag-alag variables hain.
• Code ko saaf-suthra likhne ke liye proper indentation aur spacing ka use karein.