09-if-else.md

Conditional Statements (If-Else)

In programming, we often need to execute different code based on different conditions. This is called decision making or control flow. JavaScript provides the if, else if, and else statements to handle these scenarios.

1. The if Statement

The if statement executes a block of code only if a specified condition is true.

Syntax:

if (condition) {
    // Code to execute if condition is true
}

2. The else Statement

Use else to specify a block of code to be executed if the condition is false.

Syntax:

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

Example: Voting Eligibility

let age = 18;

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

3. The else if Ladder

Use else if to specify a new condition if the first condition is false. You can chain multiple else if statements.

Syntax:

if (condition1) {
    // Code if condition1 is true
} else if (condition2) {
    // Code if condition1 is false and condition2 is true
} else {
    // Code if both conditions are false
}

Example: Student Grading System

let marks = 85;

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

4. Nested If Statements

You can have if statements inside other if statements. This is useful for checking multiple dependent conditions.

let age = 20;
let hasID = true;

if (age >= 18) {
    if (hasID) {
        console.log("Allowed to enter.");
    } else {
        console.log("Entry denied: ID required.");
    }
} else {
    console.log("Entry denied: Underage.");
}

5. Ternary Operator (Shorthand)

For simple if-else logic, you can use the Ternary Operator ?. It writes the condition in a single line.

Syntax: variable = (condition) ? value_if_true : value_if_false;

Example:

let age = 20;
let status = (age >= 18) ? "Adult" : "Minor";
console.log(status); // Outputs: "Adult"

Tip

Best Practice: Use if-else for complex logic and multiple conditions. Use the Ternary Operator only for simple, short assignments to keep your code readable.