Examples of many common algorithms (e.g. bit manipulation, Pascal’s triangle, Hamming distance) and data structures (e.g. linked lists, tries, graphs) with explanations. Available in eighteen other written languages too.
Oleksii Trekhleb et al.
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❤10
CHALLENGE
const original = {
name: 'Sarah',
hobbies: ['reading', 'coding'],
address: { city: 'Portland', zip: 97201 }
};
const shallow = { ...original };
const deep = JSON.parse(JSON.stringify(original));
shallow.name = 'Emma';
shallow.hobbies.push('hiking');
shallow.address.city = 'Seattle';
deep.hobbies.push('swimming');
deep.address.zip = 98101;
console.log(original.hobbies.length, original.address.city);❤7🤔1
❤2
Esteemed browser and Web standards expert Alex Russell looks at the state of client-side Web performance, what sort of bandwidth you should be taking into account, what devices people are using, and warns against ever-growing JavaScript bundle sizes. A lot of data here.
Alex Russell
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👍5❤1🤔1
CHALLENGE
class SimpleObservable {
constructor(subscribeFn) {
this.subscribeFn = subscribeFn;
}
subscribe(observer) {
return this.subscribeFn(observer);
}
}
const obs = new SimpleObservable(observer => {
observer.next('first');
observer.next('second');
observer.complete();
});
const results = [];
obs.subscribe({
next: val => results.push(val),
complete: () => results.push('done')
});
console.log(results.join('-'));❤4👍1🤔1
What is the output?
Anonymous Quiz
46%
first-second-done
39%
first-second-complete
10%
first-done-second
4%
done-first-second
Get a Google Calendar-style experience in your own apps. Has connectors for React, Vue and Angular, but can be used with plain JavaScript too. The base version is MIT licensed, but there’s a commercial version too with extra features.
Adam Shaw
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❤10🤩1
CHALLENGE
const arr = [1, 2, 3];
const obj = { valueOf: () => 4, toString: () => '5' };
const result1 = arr + obj;
const result2 = +obj;
const result3 = String(obj);
const result4 = obj == 4;
const result5 = obj === 4;
console.log(`${result1}|${result2}|${result3}|${result4}|${result5}`);
const weird = [] + [] + 'hello';
const weirder = [] + {} + [];
const weirdest = {} + [] + {};
console.log(`${weird}|${weirder}|${weirdest}`);
const final = !!'0' + !!'' + !!null + !!undefined;
console.log(final);
❤3
Draft diagrams quickly with TypeScript. Define your data models through top-level type aliases and interfaces and it automatically lays out the nodes in an efficient way. GitHub repo.
Andrei Neculaesei
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❤8👍1
CHALLENGE
const data = '{"users": [{"name": "Sarah", "age": 25}, {"name": "Mike", "age": null}]}';
try {
const parsed = JSON.parse(data);
const result = parsed.users.map(user => {
return user.age ?? 'unknown';
});
console.log(result.join(' - '));
} catch (error) {
console.log('Parse error occurred');
}
const invalidJson = '{"name": "John", age: 30}';
try {
JSON.parse(invalidJson);
console.log('Success');
} catch {
console.log('Invalid');
}❤8
What is the output?
Anonymous Quiz
21%
Parse error occurred, Invalid
38%
25 - null, Success
11%
25 - unknown
30%
25 - unknown, Invalid
👍6🤔2❤1
CHALLENGE
class Logger {
log(msg) {
return `[LOG]: ${msg}`;
}
}
class Formatter {
format(text) {
return text.toUpperCase();
}
}
class Service {
constructor(logger, formatter) {
this.logger = logger;
this.formatter = formatter;
}
process(data) {
const formatted = this.formatter.format(data);
return this.logger.log(formatted);
}
}
const service = new Service(new Logger(), new Formatter());
console.log(service.process('hello world'));What is the output?
Anonymous Quiz
55%
[LOG]: HELLO WORLD
27%
HELLO WORLD
10%
hello world
8%
[LOG]: hello world