Conditional Code

Conditional statements allow your program to make decisions and execute different code based on different conditions.

if Statements

The most basic conditional statement:

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

if-else Statements

Execute different code based on whether a condition is true or false:

if (condition) {
    // code to execute if condition is true
} else {
    // code to execute if condition is false
}

if-else if-else Statements

Handle multiple conditions:

if (score >= 90) {
    grade = 'A';
} else if (score >= 80) {
    grade = 'B';
} else if (score >= 70) {
    grade = 'C';
} else {
    grade = 'F';
}

Truthy and Falsy Values

In JavaScript, all values are either "truthy" or "falsy" when evaluated in a boolean context.

Falsy Values

• false
• 0
• "" (empty string)
• null
• undefined
• NaN

Truthy Values

Everything else is truthy, including:

• Non-zero numbers
• Non-empty strings
• Objects
• Arrays (even empty ones)

Ternary Operator

A shorthand way to write simple if-else statements:

let message = (age >= 18) ? 'adult' : 'minor';

Switch Statements

Use switch statements when you have many conditions to check:

switch (dayOfWeek) {
    case 'Monday':
        console.log('Start of work week');
        break;
    case 'Friday':
        console.log('TGIF!');
        break;
    default:
        console.log('Regular day');
        break;
}