Created by someone who works on graphics for the NYT, this elegant library lets you work with polygons, bounding boxes, reflection, interpolation, rotation, and the like (examples). Does one polygon intersect with another? Thereโs a function for that.
Harry Stevens (The New York Times)
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CHALLENGE
class BankAccount {
#balance;
#transactionLog = [];
constructor(initialBalance) {
this.#balance = initialBalance;
}
deposit(amount) {
this.#balance += amount;
this.#transactionLog.push(`+${amount}`);
return this;
}
withdraw(amount) {
if (amount > this.#balance) throw new Error("Insufficient funds");
this.#balance -= amount;
this.#transactionLog.push(`-${amount}`);
return this;
}
get summary() {
return `Balance: ${this.#balance} | Txns: ${this.#transactionLog.join(", ")}`;
}
}
const account = new BankAccount(100);
account.deposit(50).deposit(25).withdraw(30);
console.log(account.summary);
console.log(account.hasOwnProperty("#balance"));โค2๐1
What is the output?
Anonymous Quiz
12%
true
30%
Balance: 175 | Txns: +50, +25, -30 false
34%
Balance: 145 | Txns: +50, +25, -30
23%
Balance: 145 | Txns: +50, +25, -30 false
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CHALLENGE
class Vehicle {
#speed = 0;
constructor(type, maxSpeed) {
this.type = type;
this.maxSpeed = maxSpeed;
}
accelerate(amount) {
this.#speed = Math.min(this.#speed + amount, this.maxSpeed);
return this;
}
getStatus() {
return `${this.type} going ${this.#speed}/${this.maxSpeed} km/h`;
}
}
class ElectricVehicle extends Vehicle {
#battery;
constructor(type, maxSpeed, battery) {
super(type, maxSpeed);
this.#battery = battery;
}
accelerate(amount) {
this.#battery -= amount * 0.5;
return super.accelerate(amount);
}
getStatus() {
return `${super.getStatus()} | Battery: ${this.#battery}%`;
}
}
const ev = new ElectricVehicle("Tesla", 250, 100);
ev.accelerate(80).accelerate(200);
console.log(ev.getStatus());
console.log(ev instanceof Vehicle);
console.log(ev.constructor === ElectricVehicle);
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CHALLENGE
const compose = (...fns) => x => fns.reduceRight((acc, fn) => fn(acc), x);
const pipe = (...fns) => x => fns.reduce((acc, fn) => fn(acc), x);
const double = x => x * 2;
const addTen = x => x + 10;
const square = x => x ** 2;
const negate = x => -x;
const composed = compose(negate, square, addTen, double);
const piped = pipe(negate, square, addTen, double);
const val = 3;
console.log(composed(val)); // compose: right-to-left
console.log(piped(val)); // pipe: left-to-right
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CHALLENGE
const company = {
name: "TechCorp",
ceo: {
name: "Morgan",
address: {
city: "Berlin"
}
},
getRevenue: () => 5_000_000
};
const cfoCity = company?.cfo?.address?.city ?? "Unknown";
const ceoCity = company?.ceo?.address?.city ?? "Unknown";
const ceoCountry = company?.ceo?.address?.country ?? "N/A";
const revenue = company?.getRevenue?.() ?? 0;
const employees = company?.getEmployees?.() ?? "No data";
console.log(cfoCity, ceoCity, ceoCountry, revenue, employees);CHALLENGE
const data = [
{ name: "Zara", score: 88 },
{ name: "Liam", score: 95 },
{ name: "Maya", score: 88 },
{ name: "Omar", score: 72 },
{ name: "Nina", score: 95 },
];
const sorted = [...data].sort((a, b) =>
b.score !== a.score
? b.score - a.score
: a.name.localeCompare(b.name)
);
console.log(sorted.map(p => `${p.name}:${p.score}`).join(", "));
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