JavaScript me Conditional Statements Kya Hote Hain?

Apne Code me Decision-Making aur Logic Build Karna Sikhein.

Introduction to Conditional Statements

Conditional statements programming ka ek fundamental concept hai jo code ko decision lene ki power deta hai. Isme ek condition check ki jaati hai, aur uske `true` ya `false` hone par alag-alag code blocks execute hote hain. Yeh program ke flow ko control karne aur use dynamic banane ke liye zaroori hain.

1. The if Statement

if statement ka use tab hota hai jab aapko ek specific code block ko sirf tabhi run karna ho jab ek condition `true` ho.

if (condition) {
  // Yeh block sirf tab chalega jab condition true hogi
}

Example:

let temperature = 30;
if (temperature > 25) {
  console.log("Bahut garmi hai!"); // Output: Bahut garmi hai!
}

2. The if-else Statement

Jab `if` condition `false` ho, tab `else` block ka code execute hota hai. Yeh "agar yeh nahi, toh woh" wala logic provide karta hai.

if (condition) {
  // Jab condition true ho
} else {
  // Jab condition false ho
}

Example:

let age = 16;
if (age >= 18) {
  console.log("Aap vote de sakte hain.");
} else {
  console.log("Aap vote nahi de sakte."); // Output: Aap vote nahi de sakte.
}

3. The else-if Ladder

Jab aapko multiple conditions check karni ho, tab `else if` ka use hota hai. JavaScript ek-ek karke conditions check karta hai, aur jo bhi condition pehle `true` milti hai, uska block execute karke baaki sabko skip kar deta hai.

let marks = 75;
if (marks >= 90) {
  console.log("Aapko A grade mila.");
} else if (marks >= 80) {
  console.log("Aapko B grade mila.");
} else if (marks >= 70) {
  console.log("Aapko C grade mila."); // Output: Aapko C grade mila.
} else {
  console.log("Fail.");
}

4. The switch Statement

Jab ek hi variable ki multiple fixed values se comparison karna ho, tab `switch` statement `else-if` ladder ka ek clean aur efficient alternative hota hai.

let day = "Monday";
switch (day) {
  case "Sunday":
    console.log("Aaj holiday hai!");
    break;
  case "Monday":
    console.log("Aaj kaam shuru karo!"); // Output: Aaj kaam shuru karo!
    break;
  default:
    console.log("Invalid din!");
}

Note: Har `case` ke baad `break;` lagana zaroori hai, warna agle cases bhi execute ho jaayenge (ise "fall-through" kehte hain).

if-else vs. switch

Featureif-else Ladderswitch Statement
Best ForComplex conditions (range checks, multiple variables)Ek hi variable ki fixed values check karne ke liye
ReadabilityComplex ho sakta haiClean aur readable hota hai

Key Takeaways

  • if: Sirf ek condition check karne ke liye.
  • if-else: Do options (true ya false) ke liye.
  • else-if: Multiple alag-alag conditions check karne ke liye.
  • switch: Ek hi variable ki multiple fixed values se comparison ke liye.
Bonus: Practical Application!
Ab in statements ko practically use karke dekhein.

Ek variable `score` banayein aur `if-else-if` ka use karke alag-alag scores ke liye different messages (e.g., "Excellent", "Good", "Try Again") print karein.

Practice in JS Editor
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