How to use filter and Promise.all In Javascript
In this approach, we use Promise.all to handle the asynchronous operations and filter the array based on the results.
Example: To demonstrate filtering an array using an asynchronous function that returns a promise using filter and Promise.all
async function filterAsync(array, asyncCallback) {
const filterResults = await Promise
.all(array.map(asyncCallback));
return array
.filter((_, index) => filterResults[index]);
}
async function isEvenAsync(num) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(num % 2 === 0);
}, 100);
});
}
(async () => {
let numbers = [1, 2, 3, 4, 5, 6];
let evenNumbers = await filterAsync(numbers, isEvenAsync);
console.log("Even Numbers:", evenNumbers);
})();
Output
Even Numbers: [ 2, 4, 6 ]
Time complexity: O(n)
Auxiliary Space: O(n)
JavaScript Program to Filter an Array with a Function that Returns a Promise
Given an array, our task is to filter its elements using an asynchronous function that returns a promise. This function will determine whether an element should be included in the resulting array.
Example:
Input: numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
Output: Even Numbers: [ 2, 4, 6, 8, 10 ]
Below are the approaches to filter an array using an asynchronous function that returns a promise in JavaScript:
Table of Content
- Using filter and Promise.all
- Using for…of and await