JavaScript If Condition Fundamentals

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✅ 1. What is an if condition?

An if statement is used to execute code only when a condition is true.

📌 Syntax:

if (condition) {
    // code runs if condition is true
}

✅ Example:

let age = 18;if (age >= 18) {
    console.log("You are eligible to vote");
}

✅ 2. if...else Statement

Used when you want to handle both true and false cases.

📌 Syntax:

if (condition) {
    // true block
} else {
    // false block
}

✅ Example:

let number = 5;if (number % 2 === 0) {
    console.log("Even number");
} else {
    console.log("Odd number");
}

✅ 3. if...else if...else

Used when you have multiple conditions.

📌 Syntax:

if (condition1) {
    // block 1
} else if (condition2) {
    // block 2
} else {
    // default block
}

✅ Example:

let marks = 75;if (marks >= 90) {
    console.log("Grade A");
} else if (marks >= 70) {
    console.log("Grade B");
} else {
    console.log("Grade C");
}

✅ 4. Nested if

An if inside another if.

✅ Example:

let age = 20;
let hasLicense = true;if (age >= 18) {
    if (hasLicense) {
        console.log("You can drive");
    } else {
        console.log("Get a license first");
    }
}

✅ 5. Ternary Operator (Short if-else)

A short form of if...else.

📌 Syntax:

condition ? value1 : value2;

✅ Example:

let age = 16;let result = (age >= 18) ? "Adult" : "Minor";
console.log(result);

🔷 Important Concepts

🔹 Comparison Operators

OperatorMeaning
==Equal (loose)
===Equal (strict)
!=Not equal
!==Strict not equal
> < >= <=Comparison

👉 Always prefer === (strict equality)

🔹 Logical Operators

OperatorMeaning
&&AND
!NOT

✅ Example:

let age = 20;
let hasID = true;if (age >= 18 && hasID) {
    console.log("Allowed entry");
}

🔷 Practice Programs (Very Important 🚀)

🟢 Beginner Level

1. Check Positive or Negative

let num = -5;if (num >= 0) {
    console.log("Positive");
} else {
    console.log("Negative");
}

2. Find Largest of Two Numbers

let a = 10, b = 20;if (a > b) {
    console.log("A is larger");
} else {
    console.log("B is larger");
}

3. Check Divisible by 5

let num = 25;if (num % 5 === 0) {
    console.log("Divisible by 5");
} else {
    console.log("Not divisible");
}

🟡 Intermediate Level

4. Find Largest of Three Numbers

let a = 10, b = 25, c = 15;if (a > b && a > c) {
    console.log("A is largest");
} else if (b > c) {
    console.log("B is largest");
} else {
    console.log("C is largest");
}

5. Check Leap Year

let year = 2024;if ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0) {
    console.log("Leap Year");
} else {
    console.log("Not a Leap Year");
}

6. Grade Calculator

let marks = 85;if (marks >= 90) {
    console.log("A");
} else if (marks >= 75) {
    console.log("B");
} else if (marks >= 50) {
    console.log("C");
} else {
    console.log("Fail");
}

🔴 Advanced Level

7. Check Login Access

let username = "admin";
let password = "1234";if (username === "admin" && password === "1234") {
    console.log("Login successful");
} else {
    console.log("Invalid credentials");
}

8. Check Even/Odd using Ternary

let num = 7;let result = (num % 2 === 0) ? "Even" : "Odd";
console.log(result);

9. Traffic Light System

let color = "red";if (color === "red") {
    console.log("Stop");
} else if (color === "yellow") {
    console.log("Get Ready");
} else if (color === "green") {
    console.log("Go");
} else {
    console.log("Invalid color");
}

🔷 Pro Tips 💡

  • Use === instead of ==
  • Keep conditions simple and readable
  • Avoid deeply nested if → use else if instead
  • Use ternary only for short conditions

🔷 Practice Questions (Try Yourself )

  1. Check if a number is divisible by both 3 and 7
  2. Check whether a character is vowel or consonant
  3. Find smallest of three numbers
  4. Check if a number is palindrome
  5. Create simple ATM withdrawal condition

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