JavaScript

Sponsored by Bryntum 👮‍♀️ World Class Web Components ❓ CHALLENGE

const obj = {
  a: 1,
  b: 2
};

let a = 10;
let b = 20;

with (obj) {
  a += 1;
  b += 1;
}

console.log(a, obj.a, b, obj.b);

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Sponsored by Bryntum 👮‍♀️ World Class Web Components ✌️ JavaScript Weekly #​701

Sponsored by Bryntum 👮‍♀️ World Class Web Components ❓ CHALLENGE

const weakMap = new WeakMap();
const objs = [{}, {}, {}];

objs.forEach((obj, index) => weakMap.set(obj, index + 1));

const result = objs.filter(obj => weakMap.has(obj)).map(obj => weakMap.get(obj) * 2);

console.log(result);

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Sponsored by Bryntum 👮‍♀️ World Class Web Components ❓ CHALLENGE

const weakMap = new WeakMap();
const obj1 = {};
const obj2 = { key: 'value' };

weakMap.set(obj1, obj2);

const result = weakMap.get(obj1).key.split('').reverse().join('');

console.log(result);

Sponsored by Bryntum 👮‍♀️ World Class Web Components 😆 What about JavaScript?

Sponsored by Bryntum 👮‍♀️ World Class Web Components ❓ CHALLENGE

const weakMap = new WeakMap();
const array = [1, 2, 3];
const obj = {};

weakMap.set(obj, array);

const result = weakMap.get(obj).reduce((acc, val) => acc + val);

console.log(result);

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Sponsored by Bryntum 👮‍♀️ World Class Web Components ❓ CHALLENGE

const weakMap = new WeakMap();
const obj = {};

(function() {
  const internalObj = {};
  weakMap.set(internalObj, 'hidden');
  obj.ref = internalObj;
})();

delete obj.ref;

const result = weakMap.has(obj.ref);

console.log(result);

😭 ...

CHALLENGE

const weakMap = new WeakMap();
const array = [{}, {}];

array.forEach(obj => weakMap.set(obj, obj));
const result = array.map(obj => weakMap.get(obj) === obj);

console.log(result);

✌️ ECMAScript Safe Assignment Operator Proposal We often feature ECMAScript proposals that are in their later stages, but how about a brand new one you could get involved with? This one proposes an interesting additional bit of language syntax (`?=`) that returns a [error, value] tuple from an assignment. Arthur Fiorette

CHALLENGE

const weakMap = new WeakMap();
const gen = (function* () {
  yield { key: 'value1' };
  yield { key: 'value2' };
})();

const obj1 = gen.next().value;
const obj2 = gen.next().value;

weakMap.set(obj1, 'stored value1');
weakMap.set(obj2, 'stored value2');

const result = [...gen].map(obj => weakMap.get(obj));

console.log(result);