Conditional Statements in JavaScript

Making Decisions in Code

• In JavaScript, conditional statements are used to make decisions in a program.
• They help the program choose what action to perform based on whether a condition is true or false.
• Conditional statements make your code smart and interactive.

For example:

• If the user is 18 or older → allow voting
• Else → show not eligible message

JavaScript mainly provides these conditional statements:

• if
• if...else
• if...else if...else
• switch

Let’s understand each one with examples.

1) if Statement

The if statement is used when you want to execute a block of code only if a condition is true.

Syntax

if (condition) {
    // code to execute
}

Example

let age = 20;

if (age >= 18) {
    console.log("Eligible to vote");
}

Output

Eligible to vote

Here, since age >= 18 is true, the message gets printed.

2) else Statement

The else block runs when the condition inside if is false.

Syntax

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

Example

let age = 16;

if (age >= 18) {
    console.log("Eligible to vote");
} else {
    console.log("Not eligible to vote");
}

Output

Not eligible to vote

This is useful when there are two possible outcomes.

3) else if Statement

This is used when you need to check multiple conditions.

Syntax

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

Example

let marks = 85;

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

Output

Grade A

The program checks conditions from top to bottom and runs the first true condition.

4) switch Statement

The switch statement is used when you want to compare one variable with multiple values.

It is often cleaner than using many else if conditions.

Syntax

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

Example

let day = 3;

switch (day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    case 3:
        console.log("Wednesday");
        break;
    default:
        console.log("Invalid day");
}

Output

Wednesday

Why break is Important?

The break statement stops the switch after a matching case is found.

Without break, the code continues executing the next cases.

Example Without Break

let day = 1;

switch (day) {
    case 1:
        console.log("Monday");
    case 2:
        console.log("Tuesday");
}

Output

Monday
Tuesday

This happens because there is no break.

Real-Life Example

1.

let temperature = 35;

if (temperature > 30) {
    console.log("It's hot outside");
} else {
    console.log("Weather is cool");
}

• Conditional statements help programs make decisions just like humans do.

2.

let team = "CSK";

if (team === "MI") {
    console.log("Mumbai Indians");
} 
else if (team === "CSK") {
    console.log("Chennai Super Kings");
} 
else if (team === "RCB") {
    console.log("Royal Challengers Bengaluru");
} 
else {
    console.log("Invalid Team");
}

Conclusion

Conditional statements are one of the most important concepts in JavaScript.

They help in:

• decision making
• validating inputs
• checking conditions
• controlling program flow