Implement custom Promise.all()

Saurav Gupta — Thu, 05 Aug 2021 05:47:46 +0000

Promise.myAll = function (values) {
  return new Promise((resolve, reject) => {
    let results = [];
    let completed = 0;
    values.forEach((singlePromise, index) => {
      singlePromise
        .then((res) => {
          results[index] = res;
          completed++;
          if (completed === values.length) resolve(results);
        })
        .catch((e) => {
          reject(e);
        });
    });
  });
};

function task(time) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(time), time);
  });
}

const taskList = [task(1000), task(5000), task(3000)];

Promise.myAll(taskList)
  .then((results) => {
    console.log("got results", results);
  })
  .catch(console.error);

Different ways to Flatten the array in JavaScript

Saurav Gupta — Wed, 04 Aug 2021 09:05:19 +0000

Using Reduce

function flatten(arr) {
  return arr.reduce((acc, item) => {
    if (Array.isArray(item)) {
      acc = [...acc, ...flatten(item)];
    } else {
      acc.push(item);
    }
    return acc;
  }, []);
}

Using Recursion

function flattenRecursion(arr) {
  if (!arr.length) return [];
  let res = [];
  for (let i = 0; i < arr.length; i++) {
    const item = arr[i];
    if (Array.isArray(item)) {
      res = [...res, ...flattenRecursion(item)];
    } else {
      res.push(item);
    }
  }
  return res;
}

DEV Community: Saurav Gupta

Implement custom Promise.all()

Different ways to Flatten the array in JavaScript

Using Reduce

Using Recursion