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CHALLENGE
const wm = new WeakMap();
const obj1 = { name: 'first' };
const obj2 = { name: 'second' };
const obj3 = obj1;
wm.set(obj1, 'value1');
wm.set(obj2, 'value2');
wm.set(obj3, 'value3');
console.log(wm.get(obj1));
console.log(wm.get(obj2));
console.log(wm.get(obj3));
console.log(wm.has(obj1));
console.log(wm.size);
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What is the output?
Anonymous Quiz
20%
value3 value2 value3 true 3
31%
value3 value2 value3 true undefined
35%
value1 value2 value1 true undefined
14%
value1 value2 value3 true 2
๐6๐ฅ3
CHALLENGE
class CustomError extends Error {
constructor(message) {
super(message);
this.name = 'CustomError';
}
}
try {
throw new CustomError('Something went wrong');
} catch (e) {
console.log(e instanceof Error);
console.log(e instanceof CustomError);
console.log(e.constructor.name);
console.log(e.name);
}๐1
What is the output?
Anonymous Quiz
24%
true, false, Error, CustomError
33%
false, true, CustomError, Error
37%
true, true, CustomError, CustomError
7%
true, true, Error, Error
๐6โค3๐ฅ2
CHALLENGE
class EventEmitter {
constructor() {
this.events = {};
}
on(event, callback) {
this.events[event] = this.events[event] || [];
this.events[event].push(callback);
return this;
}
emit(event, data) {
if (this.events[event]) {
this.events[event].forEach(cb => cb(data));
}
return this;
}
}
class Logger {
log(msg) { console.log(`[LOG]: ${msg}`); }
}
class DataProcessor {
constructor(emitter, logger) {
this.emitter = emitter;
this.logger = logger;
this.emitter.on('process', (data) => {
this.logger.log(data.toUpperCase());
});
}
process(data) {
this.emitter.emit('process', data);
}
}
const emitter = new EventEmitter();
const logger = new Logger();
const processor = new DataProcessor(emitter, logger);
processor.process('hello world');
emitter.emit('process', 'composition rocks');1๐4โค1
What is the output?
Anonymous Quiz
39%
[LOG]: HELLO WORLD [LOG]: COMPOSITION ROCKS
36%
[LOG]: COMPOSITION ROCKS [LOG]: hello world
15%
[LOG]: composition rocks [LOG]: HELLO WORLD
10%
[LOG]: hello world [LOG]: composition rocks
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Did you know the Node.js project maintains a page about security best practices organized around how to mitigate ten of the most significant vectors? Topics include networking weaknesses, timing attacks, supply chain attacks, and the monkey patching of intrinsics.
Node Documentation
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โค3๐1๐ฅ1
CHALLENGE
const obj = { count: 0 };
const arr = [obj, obj, obj];
function increment(item) {
item.count++;
return item;
}
const results = arr.map(increment);
console.log(obj.count);
console.log(results[0] === results[1]);
console.log(results.length);
console.log(arr[0].count);3โค6
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Think something like Plausible or Google Analytics, but built in Node and ready for you to host yourself. Hereโs the full feature list. MIT licensed but also available as a paid hosted service.
Umami Software, Inc.
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โค7๐ฅ1
Created at Pixar in the 80s, the RenderMan Interface Specification was an early API for building 3D scenes. Anders has been building a Node-based, 90s-style renderer for the format โas a stroll down amnesia laneโ in pure JavaScript.
Anders Brownworth
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๐2๐ฅ2โค1
CHALLENGE
const data = '{"name":"Sarah","age":25,"skills":["JavaScript","Python"]}'
const parsed = JSON.parse(data)
const stringified = JSON.stringify(parsed, null, 0)
const reparsed = JSON.parse(stringified)
try {
const invalid = '{name:"John","incomplete":}'
JSON.parse(invalid)
} catch (e) {
console.log(e.name)
}
console.log(typeof parsed.age)
console.log(reparsed.skills.length)
console.log(JSON.stringify({a: undefined, b: null, c: 0}))What is the output?
Anonymous Quiz
23%
SyntaxError number 2 {"b":null,"c":0}
47%
TypeError string 2 {"a":undefined,"b":null,"c":0}
27%
SyntaxError number 2 {"a":null,"b":null,"c":0}
4%
ReferenceError number 2 {"b":null,"c":0}
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๐ฏ๐ต Fancy writing JavaScript in Japanese (above)? Say ใใใซใกใฏ to KokoScript.
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