10 Simple Javascript For-Loop Exercises

Here 10 simple javascript For-Loop Exercises to test your introductory-level understanding of Javascript For-Loops. Use for-loops in all of your solutions below.

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Exercise 1)

Get the sum of two arrays…actually the sum of all their elements.
P.S. Each array includes only integer numbers. Output is a number too.

let arr_1 = [3, 5, 22, 5,  7,  2,  45, 75, 89, 21, 2]; // --> 276
let arr_2 = [9, 2, 42, 55, 71, 22, 4,  5,  90, 25, 26]; // --> 351
// Example output: 
// 276 + 351 = 627

Exercise 2)

Using a for loop print all even numbers up to and including n. Don’t include 0.

let n1 = 22; 
// Example output: 
// 2 4 6 8 10 12 14 16 18 20 22 OR each item on a new line
 

Exercise 3)

Using a for loop output the elements in reverse order

let arr = [43, "what", 9, true, "cannot", false, "be", 3, true];
// Example output: 
// true 3.5  be  false cannot  true 9 what 43 OR each item on a new line

Exercise 4)

Given two arrays of integers. Add up each element in the same position and
create a new array containing the sum of each pair. Assume both arrays are of the same length.

 
let arr_3   = [4, 6, 7];
let arr_4    = [8, 1, 9];
// Example output: 
// [12, 7, 16]

Exercise 5)

Given a string change the every second letter to an uppercase ‘Z’. Assume
there are no space.

let str1 = "javascript";  
// Example output: 
// jZvZsZrZpZ OR each letter on a new line
// HINT: You can use  if((i+1) % 2 == 0) to check for even indexes 

Exercise 6)

Check if a string contains the letter “y”. Print “yes” if it does and “no” if it does not.

let str2 = "don’t know why";
// Example output: 
// “yes” 

Exercise 7)

Given a number n Calculate the factorial of the number

let n2 = 4; //  4 * 3 * 2 * 1 = 24
// Example output:
// 24

Exercise 8)

Write a program that will allow someone to guess a four digit pin exactly 4
times. If the user guesses the number correctly. It prints “That was
correct!” Otherwise it will print “Sorry that was wrong.” Program stops after the 4th attempt of if they got it right.

let pin = 0704;
// Example output:
// Please make your guess: 
// 4544 
// Sorry that was wrong.
// Please make your guess: 
// 4444
// Sorry that was wrong.
// Please make your guess: 
// 0704
// That was correct!

Exercise 9)

Write a program that will check if two strings are palindromes. A palindrome is a word that spells the same forward and backward.
Palindrome: a word, phrase, or sequence that reads the same backward as
forward, e.g., madam or nurses run.

let str3 = "racecar";
let str4 = "Java";
// Example output:
// string1 palindrome?: 
// Yes 
// string2 palindrome?: 
// No 

Exercise 10)

This is a code wars kata. click here to train on “Grasshopper – Summation” on
code wars. Write a program that finds the summation of every number from 1 to num. The number will always be a positive integer greater than 0.

let num1 = 2; 
let num2 = 8; 
// Example output: 
// 1 + 2 = 3
// 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 36 

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