JavaScript

❓ CHALLENGE

const numbers = [1, 2, 3, 4, 5];

const result = numbers.filter(num => num % 2 === 0)
                     .map(num => num ** 2)
                     .reduce((acc, val) => acc + val, 0);

console.log(result);

😂

🤟 💚 The Node.js Valentine's Day Security Releases Security releases had been expected to land in the past week for Node and they’re now here as v21.6.2 (Current), v20.11.1 (LTS), and v18.19.1 (LTS). They include fixes for a variety of vulnerabilities, including some high severity ones involving HTTP-based DoS attacks and privilege escalation. RAFAEL GONZAGA AND MARCO IPPOLITO

❓ CHALLENGE *

const string = "Lorem ipsum dolor sit amet";

const result = string.split(" ")
                     .map(word => word.toLowerCase())
                     .reduce((acc, word) => {
                       acc[word] = (acc[word] || 0) + 1;
                       return acc;
                     }, {});

console.log(result);

💥 Questions by roadmap.sh roadmap.sh is the 6th most starred project on GitHub and is visited by hundreds of thousands of developers every month.

❓ CHALLENGE

function recursiveMaxSubarraySum(nums, startIndex = 0, currentSum = 0, maxSum = -Infinity) {
  if (startIndex === nums.length) {
    return maxSum;
  }

  currentSum = Math.max(nums[startIndex], currentSum + nums[startIndex]);
  maxSum = Math.max(currentSum, maxSum);

  return recursiveMaxSubarraySum(nums, startIndex + 1, currentSum, maxSum);
}

const result = recursiveMaxSubarraySum([-2, 1, -3, 4, -1, 2, 1, -5, 4]);

console.log(result);

⭐️ Updates from the TC39 meeting in February 2024 Stage changes: - Several proposals advanced to stage 1. - Stage 2: “Promise.try” - Stage 3: “Uint8Array to/from base64 and hex” - Stage 4: “ArrayBuffer.prototype.transfer and friends” - Several proposals became inactive. New ECMAScript proposal stage: 2.7 🟨 “Stage 2.7 is equivalent to what we used to call Stage 3. It means that the design is considered complete, we have a full specification, and we need to write code (tests and non-polyfill implementations) to gain feedback and make progress. It’s a strong signal.” 🟨“Stage 3 has been strengthened and now also means that test262 conformance tests are ready. This is a useful signal to JS engines that a proposal is truly ready to be implemented.” 🟨“Why did we do this? We separated out the ‘Approved in Principle: Spec Ready’ stage from the later ‘Recommended for Implementation: Tests Ready’ stage to reduce wasted effort in writing tests before spec stability, whilst also clarifying the test readiness message to engines.” TC39 member Jordan Harband comments: “[Stage 2.7 is] explicitly without the signal that it’s safe to ship unflagged, or use in production (which includes publishing polyfills). Stage 3 remains the signal for these things.” ecmascript.new

❓ CHALLENGE

const numbers = [1, 2, 3, 4, 5];

const sum = numbers.reduce((acc, curr) => {
  setTimeout(() => {
    acc += curr;
  }, 0);
  return acc;
}, 0);

console.log(sum);

👀🔵 React.memo is great. but sometimes, you shouldn't use it Hovhannes

❓ CHALLENGE

function recursiveNQueens(n) {
  const board = Array.from({ length: n }, () => Array.from({ length: n }, () => "."));

  const solutions = [];

  const isSafe = (row, col) => {
    for (let i = 0; i < row; i++) {
      if (board[i][col] === "Q") return false;
      const colOffset = row - i;
      if (col - colOffset >= 0 && board[i][col - colOffset] === "Q") return false;
      if (col + colOffset < n && board[i][col + colOffset] === "Q") return false;
    }
    return true;
  };

  const placeQueens = (row) => {
    if (row === n) {
      solutions.push(board.map(row => row.join("")));
      return;
    }
    for (let col = 0; col < n; col++) {
      if (isSafe(row, col)) {
        board[row][col] = "Q";
        placeQueens(row + 1);
        board[row][col] = ".";
      }
    }
  };

  placeQueens(0);

  return solutions;
}

const result = recursiveNQueens(4);

console.log(result);

❓ CHALLENGE

function recursivePascalTriangle(n, row = [1], triangle = []) {
  triangle.push(row);
  if (n === triangle.length) {
    return triangle;
  }
  const nextRow = [1];
  for (let i = 1; i < row.length; i++) {
    nextRow.push(row[i] + row[i - 1]);
  }
  nextRow.push(1);
  return recursivePascalTriangle(n, nextRow, triangle);
}

const result = recursivePascalTriangle(5);

console.log(result);

❓ CHALLENGE

function* generatorQuiz() {
  yield 1;
}

const generator = generatorQuiz();

setTimeout(() => console.log(generator.next().value), 0);

for (const value of generator) {
  console.log(value);
}

👀 Take a Qwik Break from React with Astro Paul Scanlon compares React to Qwik using several examples and concludes that Qwik is at least worth exploring as a React alternative. PAUL SCANLON