Ternary Expressions in JavaScript: A Compact Alternative to if...else

let score = 82;
let grade = score >= 90 ? "A" : score >= 75 ? "B" : score >= 60 ? "C" : "F";
console.log(grade);
// "B"

// 😱 This is legal… but please don't:
let label = a ?(b ? "ab" : "a") :(c ? "c" : "none");

// ✅ Perfect ternary — simple value choice
let fee = isMember ? 0 : 50;
// ✅ Perfect if…else — multiple actions per branch
if (isMember) {
  applyDiscount();
  showMemberBadge();
  logActivity("member checkout");
} else {
  showSignupOffer();
  trackEvent("guest checkout");
}

// ❌ SyntaxError — there is no "if without else" in ternary land:let status = isReady ? "Go!";
// ✅ Both branches are mandatory:let status = isReady ? "Go!" : "Wait…";

// ❌ Legal but ugly — ternaries shouldn't DO things:isLoggedIn ? console.log("Hi") : console.log("Bye");
// ✅ Clear intent with if…else:if (isLoggedIn) {  console.log("Hi");} else {  console.log("Bye");}

let age = 20;
// 😱 Without parentheses, this can misbehave:
let msg = "Adult: " + age >= 18 ? "yes" : "no";
// BUG!
// ✅ Always wrap the condition:
let msg2 = "Adult: " +(age >= 18 ? "yes" : "no");
console.log(msg2);
// "Adult: yes"

// 😬 Inconsistent types — confusing downstream:
let result = isVip ? 0 : "50";
// number OR string?!
// ✅ Keep branch types consistent:
let result2 = isVip ? 0 : 50;
// both numbers ✅

// 🚚 Delivery Fee Calculator — ternaries in action
let orderTotal = 650;
let isMember = true;
let distance = 12;
// km
// Fee rules — three ternary decisions working together
let baseFee = orderTotal >= 500 ? 0 : 49;
// free over ₹500
let distanceFee = distance > 10 ? 30 : 0;
// long-distance charge
let memberDiscount = isMember ? 20 : 0;
// members save ₹20
let finalFee = baseFee + distanceFee - memberDiscount;
finalFee = finalFee < 0 ? 0 : finalFee;
// never go negative!
console.log(`Order: ₹${orderTotal}`);
console.log(`Membership: ${isMember ? "Yes ⭐" : "No"}`);
console.log(`Delivery fee: ${finalFee === 0 ? "FREE! 🎉" : "₹" + finalFee}`);

Order: ₹650Membership: Yes ⭐Delivery fee: ₹10