JavaScript Conditionals

• Conditional statements help programs make decisions.
• They run different code when a condition is true or false.
• If it is raining, take an umbrella.
• If you are hungry, eat food.
• If the traffic light is green, move forward.

Why Are Conditional Statements Important?

• React to different values and situations.
• User login systems
• Form validation
• Age verification
• Online shopping discounts
• Access control and permissions

The if Statement

• if is the simplest conditional statement.
• Its code runs only when the condition is true.

let age = 20;

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

You are eligible to vote.

• The if block runs because age is 18 or higher.

The if...else Statement

• if runs when the condition is true.
• else runs when the condition is false.

let age = 16;

if (age >= 18) {
    console.log("You can vote.");
} else {
    console.log("You cannot vote yet.");
}

You cannot vote yet.

• The else block runs because age is below 18.

The if...else if...else Statement

• Use else if to check multiple conditions.
• JavaScript runs the first matching block.

let score = 85;

if (score >= 90) {
    console.log("Grade A");
} else if (score >= 75) {
    console.log("Grade B");
} else if (score >= 60) {
    console.log("Grade C");
} else {
    console.log("Grade D");
}

Grade B

• The Grade B block is the first condition that matches.

The switch Statement

• Use switch to compare one value with multiple options.
• break stops execution after a matching case.
• default runs when no case matches.

let day = "Monday";

switch (day) {
    case "Monday":
        console.log("Start of the week");
        break;

    case "Friday":
        console.log("Weekend is near");
        break;

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

Start of the week

Nested Conditional Statements

• A conditional can contain another conditional.
• This is called a nested conditional.

let isLoggedIn = true;
let isAdmin = true;

if (isLoggedIn) {
    if (isAdmin) {
        console.log("Welcome Admin");
    }
}

Key Takeaways

• Use if for one condition.
• Use if...else for two possible paths.
• Use else if for multiple conditions.
• Use switch when one value has several possible matches.