CHALLENGE
class Registry {
static #instances = new Map();
static #count = 0;
static defaultTTL;
static maxSize;
static {
Registry.defaultTTL = 3600;
Registry.maxSize = 100;
Registry.#instances.set("__init__", { ts: 0 });
Registry.#count = Registry.#instances.size;
}
static register(key) {
if (Registry.#count >= Registry.maxSize) return false;
Registry.#instances.set(key, { ts: Registry.defaultTTL });
Registry.#count++;
return true;
}
static info() {
return `count=${Registry.#count}, ttl=${Registry.defaultTTL}, max=${Registry.maxSize}`;
}
}
Registry.register("service-a");
Registry.register("service-b");
console.log(Registry.info());๐ค3โค1
What is the output?
Anonymous Quiz
20%
count=2, ttl=3600, max=100
32%
count=1, ttl=3600, max=100
25%
count=3, ttl=undefined, max=100
23%
count=3, ttl=3600, max=100
One of the yearโs big moves in JS tooling, as told by Evan himself. The company he founded to build Vite, Vitest, Rolldown, Oxc, etc. is joining Cloudflare. Heโs candid about why (monetization is hard). Good news: all projects stay MIT-licensed, and Evan and co remain in charge.
Evan You
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CHALLENGE
const handler = {
get(target, prop, receiver) {
if (prop in target) {
return Reflect.get(target, prop, receiver) * 2;
}
return `missing:${prop}`;
},
set(target, prop, value) {
if (typeof value !== "number") {
throw new TypeError("Only numbers allowed");
}
Reflect.set(target, prop, value + 10);
return true;
},
has(target, prop) {
return prop.startsWith("x") ? false : prop in target;
},
};
const store = new Proxy({ xray: 5, zoom: 8 }, handler);
store.nova = 3;
console.log(store.xray);
console.log(store.nova);
console.log(store.ghost);
console.log("zoom" in store);
console.log("xray" in store);โค1
What is the output?
Anonymous Quiz
15%
5 13 missing:ghost true false
35%
10 13 missing:ghost false true
27%
10 26 missing:ghost true true
23%
10 26 missing:ghost true false
โค1๐ค1
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"));โค2
What is the output?
Anonymous Quiz
13%
true
33%
Balance: 175 | Txns: +50, +25, -30 false
26%
Balance: 145 | Txns: +50, +25, -30
28%
Balance: 145 | Txns: +50, +25, -30 false
๐ฅ3
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