🎉 Everything is free here. Read more →
Tutorial
JavaScript Tutorial
Revision 5

Arrays PS

🎉

Read This on Github

This article is available on Github. You can read it there and contribute to it.
Github Link
Any Issue ?

⭐ Arrays Practice Problems

Example with Explanation

  1. Create an array of numbers and take input from the user to add numbers to this array
  2. Keep adding numbers to the array in 1. until 0 is added to the array
  3. Filter for numbers divisible by 10 from a given array
  4. Create an array of square of given numbers
  5. use reduce to calculate factorial of a given number from an array of first n natural numbers( n being the number whose factorial to calculated)

⭐ Solutions

Example with Explanation

  1. Create an array of numbers and take input from the user to add numbers to this array
let arr = []; // create an empty array
let input = prompt("Enter numbers to add to the array separated by space"); // ask for user input
if (input !== null) { // check if input is not null
  // if the user clicks cancel, the input will be null and we don't want to process it
  let inputArr = input.split(" "); // split the input string by space and create an array of elements
  // the split method takes a separator as an argument and returns an array of substrings that are separated by that separator in the original string
  // for example, "12 13 14 15".split(" ") will return ["12", "13", "14", "15"]
  arr = arr.concat(inputArr); // concatenate the two arrays and assign it to arr
  // the concat method takes one or more arrays as arguments and returns a new array that contains all the elements from those arrays in order
  // for example, [1,2].concat([3,4]) will return [1,2,3,4]
}
console.log(arr); // show the array in console
// the console.log method prints a value to the browser's console which can be accessed by pressing F12 or Ctrl+Shift+I on most browsers

  1. Keep adding numbers to the array in 1. until 0 is added to the array

    let arr = []; // create an empty array
let input; // declare a variable to store user input
do {
 input = prompt('Enter numbers to add to the array separated by space, or enter 0 to stop'); // ask for user input
 arr.push(input); // add the input to the end of the array
} while (input !== '0'); // continue looping as long as the input is not 0
console.log(arr); // show the array in console

  2. Filter for numbers divisible by 10 from a given array

let arr = [25, 26, 24, 23, 20];
let filter = arr.filter((z) => {
  return z % 10 ==0;
});

console.log(filter);
let arr = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]; // create an array of numbers
let filteredArr = arr.filter((num) => num % 10 === 0); // filter the array to get numbers divisible by 10
// the filter method takes a callback function as an argument and returns a new array that contains all the elements for which the callback function returns true
// for example, [1,2,3,4,5].filter((num) => num % 2 === 0) will return [2,4]
console.log(filteredArr); // show the filtered array in console
  1. Create an array of square of given numbers
// Declare a variable named arr and assign it an array of numbers
let arr = [1, 2, 3, 4, 5];
 
// Declare a variable named filter and assign it the result of calling the map() method on arr
// The map() method takes a function as a parameter and applies it to each element of arr
// The function takes a parameter named z and returns the square of z
let filter = arr.map((z) => {
  return z * z;
});
 
// Print the value of filter to the console
// filter is an array of square of numbers from arr
console.log(filter); // [1, 4, 9, 16, 25]
  1. use reduce to calculate factorial of a given number from an array of first n natural numbers( n being the number whose factorial to calculated)
// Declare a variable named arr and assign it an array of numbers
let arr = [1, 2, 3, 4, 5];
 
// Declare a variable named filter and assign it the result of calling the reduce method on arr
// The reduce method takes a function as a parameter and applies it to each pair of elements of arr
// The function takes two parameters named z1 and z2 and returns the product of z1 and z2
let filter = arr.reduce((z1, z2) => {
  return z1 * z2;
});
 
// Print the value of filter to the console
// filter is the product of all the numbers in arr
console.log(filter); // 120

⚡ Playground

What si Node js and course Introduction Basic theory of node js Installation and setup First script program with node js Fundaments of node js Core module in Node js Make basic server in node js What is the package.json file and use in node js Small challenge for you What is Nodemon in node js Make Simple API in node js Input from command line Show file List with file system Curd with file system Asynchronous Node js Handle Asynchronous Data in Node js How Node js Works Express js Introduction Routing with express js Render html in node js Make HTML pages in node js Remove file extension Template Engine ejs Dynamic page in node js Middleware node js Route level middleware Install Mongodb for node Basics of MongoDB CURD operation with MongoDB Connect Mongodb with node Read data from MongoDB to node js Insert data from MongoDB to node js Update data from MongoDB to node js Read data from MongoDB to node js 3GET API with MongoDB and node js 3POST API method with node js and MongoDB PUT API in node js and mongo DB DELETE API in node js and mongo DB Node js mongoose CRUD operations with node js and mongoose POST API with node js and mongoose GET, DELETE AND PUT APIs with node js and mongoose Search API with node js and mongoose CRUD operations with node js and mongoose OS module node js CRUD operations in node js Events and event emitter in node js REPL in node js Node js with MySQL connection POST API with node and MySQL PUT API with node js and MySQL DELETE API with node js and MySQL Node js vs PHP

Array MethodsReact Tutorial