❓ 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 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);

👀🔵 React.iss.onemo is great. but sometimes, you shouldn't use it

Hovhannes

❓ CHALLENGE

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

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

console.log(sum);

⭐️ 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

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);

💥 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 *

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);

🤟 💚 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 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);

🤩 Tabulator: An Interactive Table and Data Grid Library

Supports all major browsers and can be used with Angular, Vue, and React if you wish. Been around for several years now, but continues to be maintained.

OLI FOLKERD