promise.all for one promise code example

Example 1: javascript promise.all

try {
    const [res1, res2, res3] = await Promise.all([
      Promise1,
      Promise2,
      Promise3,
    ]);
  } catch (err) {
    console.error(err);
  }

Example 2: promise all

Promise.all([Promise1, Promise2, Promise3])
 .then(result) => {
   console.log(result)
 })
 .catch(error => console.log(`Error in promises ${error}`))

Example 3: Promise.all

const promise1 = Promise.resolve(3);
const promise2 = 42;
const promise3 = new Promise(function(resolve, reject) {
  setTimeout(resolve, 100, 'foo');
});

Promise.all([promise1, promise2, promise3]).then(function(values) {
  console.log(values);
});
// expected output: Array [3, 42, "foo"]

Example 4: javascript promise.all

// PARALLEL PROMISES
async function fetchMoviesAndCategories() {
  const [moviesResponse, categoriesResponse] = await Promise.all([
    fetch('/movies'),
    fetch('/categories')
  ]);

  const movies = await moviesResponse.json();
  const categories = await categoriesResponse.json();

  return [movies, categories];
}

Example 5: promise all in promise all

var arr = [
  {subarr: [1,2,3]},
  {subarr: [4,5,6]},
  {subarr: [7,8,9]}
];
function processAsync(n) {
  return new Promise(function(resolve) {
    setTimeout(
      function() { resolve(n * n); },
      Math.random() * 1e3
    );
  });
}
Promise.all(arr.map(function(entity){
  return Promise.all(entity.subarr.map(function(item){
    return processAsync(item);
  }));
})).then(function(data) {
  console.log(data);
});