Ternary Operator (Conditional Operator)

A shorthand for if-else conditions. Think of it as a compact decision-making tool.

// Syntax: condition ? valueIfTrue : valueIfFalse

// Simple example
let age = 17;
let canVote = age >= 18 ? "Yes" : "No";  // "No"

// Nested ternary (use with caution - can be hard to read)
let timeOfDay = 14;  // 24-hour format
let greeting = timeOfDay < 12 ? "Good morning" :
               timeOfDay < 18 ? "Good afternoon" :
               "Good evening";  // "Good afternoon"

// Ternary in template literals
let status = "active";
let statusDisplay = `User status: ${status === "active" ? "✓ Active" : "✗ Inactive"}`;

// Alternative to if/else with side effects
function displayWelcome(user) {
    const welcomeEl = document.getElementById("welcome");
    user.isLoggedIn
        ? welcomeEl.textContent = `Welcome back, ${user.name}!`
        : welcomeEl.textContent = "Please log in";
}

Type Operators

These operators help you work with JavaScript's dynamic typing system.

// typeof operator - returns a string indicating the type
console.log(typeof 42);          // "number"
console.log(typeof "hello");     // "string"
console.log(typeof true);        // "boolean"
console.log(typeof undefined);   // "undefined"
console.log(typeof null);        // "object" (historical JavaScript quirk/bug)
console.log(typeof {});          // "object"
console.log(typeof []);          // "object" (arrays are objects in JavaScript)
console.log(typeof function(){}); // "function"

// instanceof operator - checks if an object is an instance of a class
let arr = [1, 2, 3];
let obj = { prop: "value" };
let date = new Date();

console.log(arr instanceof Array);   // true
console.log(obj instanceof Object);  // true
console.log(date instanceof Date);   // true
console.log(arr instanceof Object);  // true (arrays inherit from Object)
console.log(date instanceof Array);  // false

Optional Chaining Operator (?.)

Modern JavaScript operator that safely accesses nested properties without causing errors if a property doesn't exist.

// Problem without optional chaining
let user = {}; // User with no address property
// This would cause an error:
// let city = user.address.city; // TypeError: Cannot read property 'city' of undefined

// Traditional safe approach
let city;
if (user && user.address && user.address.city) {
    city = user.address.city;
} else {
    city = "Unknown";
}

// With optional chaining
let cityWithChaining = user?.address?.city ?? "Unknown"; // "Unknown"

// It also works with methods
let userFunction = user?.getFullName?.() ?? "No name available";

// And with array elements
let firstItem = someArray?.[0] ?? "No items";