Conditional Statements in JavaScript

Conditional statements allow your program to decide:

• Which code should run
• Which code should be skipped
• How the flow of execution should behave

What Are Conditional Statements?

Conditional statements are used to control the flow of execution in a program.

In simple terms, they help your program think like this:

• If something is true → do this
• Otherwise → do something else

1. if Statement

The if statement is the most basic control statement. It is used when you want to execute a block of code only when a condition is true.

Syntax:

if (condition) {
    // code to execute
}

Example:

let marks = 60;
if (marks >= 50) {
    console.log("You passed the exam");
}

• The condition marks >= 50 is checked
• If it is true, the code inside the block runs
• If it is false, nothing happens

2. if…else Statement

The if…else statement is used when you want to handle both cases:

• When the condition is true
• When the condition is false

when condition is true, if block will be executed otherwise else block will be executed.

Syntax:

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

Example:

let age = 15;
if (age >= 18) {
    console.log("You are eligible to vote");
} else {
    console.log("You are not eligible to vote");
}

• If the condition is true → if block runs
• If the condition is false → else block runs
• Only one block executes at a time

3. if else if Statement

When you need to check multiple conditions, you use else if.

Syntax:

if (condition1) {
    // code
} else if (condition2) {
    // code
} else if (condition3) {
    // code
} else {
    // default code
}

Example:

let marks = 82;

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

• Conditions are checked from top to bottom
• As soon as one condition becomes true, that block executes
• Remaining conditions are skipped

4. Nested Conditions

Nested conditions mean placing one if statement inside another if statement.

This is useful when one condition depends on another.

Example:

let age = 20;
let hasID = true;

if (age >= 18) {
    if (hasID) {
        console.log("Entry allowed");
    } else {
        console.log("ID is required");
    }
} else {
    console.log("Entry not allowed");
}

• First condition checks age
• If true, then second condition checks ID
• If first condition is false, inner condition is never executed

Nested conditions are useful in applications like:

• Login systems
• Payment verification
• User authentication

5. switch Statement

The switch statement is used when you have multiple conditions based on a single value.

It is often cleaner than writing many else if statements. It is mainly used when we have to check only equal condition(==).

Syntax:

switch (value) {
    case value1:
        // code
        break;
    case value2:
        // code
        break;
    default:
        // default code
}

Example:

let day = 4;

switch (day) {
    case 1:
        console.log("Monday");
        break;

    case 2:
        console.log("Tuesday");
        break;

    case 3:
        console.log("Wednesday");
        break;

    case 4:
        console.log("Thursday");
        break;

    default:
        console.log("Invalid day");
}

• The value of day is compared with each case
• When a match is found, that block executes
• break stops further execution
• If no case matches, the default block runs

6. Truthy and Falsy Values in JavaScript

In JavaScript, conditions do not always use only true or false.

Some values are automatically treated as:

• Truthy (true-like)
• Falsy (false-like)

Falsy Values

These values are always treated as false:

• False
• 0
• “”
• Null
• Undefined
• NaN

Example:

let data = "";

if (data) {
    console.log("Data exists");
} else {
    console.log("No data found");
}

• Empty string “” is falsy
• So the else block executes

Truthy Values

All other values are considered truthy:

• “Hello”
• 1
• -10
• []
• {}
• “0”

Example:

let username = "Ritik";

if (username) {
    console.log("User is logged in");
}

• Non-empty string is truthy
• So the condition becomes true

Why Truthy and Falsy Are Important?

if (userEmail) {
    console.log("Email exists");
}

Instead of writing:

if (userEmail === true)

This makes code simpler and more readable.

Example:

let userLoggedIn = true;
let isPremiumUser = false;

if (userLoggedIn) {
    if (isPremiumUser) {
        console.log("Access all features");
    } else {
        console.log("Limited access");
    }
} else {
    console.log("Please login first");
}

Conclusion

Control statements are one of the most important parts of JavaScript.

They help you:

• Build logic
• Make decisions
• Create real applications

You should clearly understand:

• if, else, else if
• Nested conditions
• switch statement
• Truthy and falsy values

Without these concepts, programming is incomplete.