Iteration-with-the-while-Loop

Week 1 - Iteration with the while Loop

Basic Requirments

1.Summation to n: Let's implement the function sum that takes a single parameter n, and computes the sum of all integers up to n starting from 0, e.g.:

 function sum(n) { 
 // TODO: your code here 
 } 
 sum(3); // => 6 
 sum(4); // => 10 
 sum(5); // => 15

2.Factorial of n: The factorial of n is the product of all the integers preceding n, starting with 1, e.g.:

 function factorial(n) { 
 // TODO: your code here 
 } 
 factorial(3); // => 6 
 factorial(4); // => 24 
 factorial(5); // => 120

3.Repeating a String n Times: Let's write a function called repeatString that takes two parameters: a string str, which is the string to be repeated, and count -- a number representing how many times the string s should be repeated, e.g.

 function repeatString(str, count) { 
 // TODO: your code here 
 } 
 repeatString('dog', 0); // => '' 
 repeatString('dog', 1); // => 'dog' 
 repeatString('dog', 2); // => 'dogdog' 
 repeatString('dog', 3); // => 'dogdogdog'

Your task is to implement the repeatString function using a while loop.

More Practice

1.Go back through any of the exercises done in the introduction to repetition and refactor them to use the while loop.

2.Fencepost Loop: Use a while loop to build a single string with the numbers 1 through n, separated by commas. Have it return the new string. How can we make sure not to have a comma after the last number?

 function counting(n) { 
       // TODO: your code here 
 } 
 counting(5); // => '1, 2, 3, 4, 5' 
 counting(1); // => '1' 
 counting(3); // => '1, 2, 3'

3.Meet & Greet: n numbers are coming to a party for numbers. Introduce them each to all the guests as they arrive. You should end up with output looking something like this one for n = 5:

 welcome 1 
 welcome 2, meet 1 
 welcome 3, meet 1 and 2 
 welcome 4, meet 1, 2 and 3 
 welcome 5, meet 1, 2, 3 and 4

HINT: search for which symbol that creates a line break in a string.

4.Reverse String: Write a function that takes a string as an input and returns the reverse of that string.

 function reverseString(str) { 
       // TODO: your code here 
 } 
 reverseString('hello'); // => 'olleh' 
 reverseString('1#*$'); // => '$*#1'

Do this using a while loop.

5.Write a javascript program to print all Prime numbers from 1 to n.

6.Write a JavaScript for loop that will iterate from 0 to n. For each iteration, it will check if the current number is odd or even, and display a message to the screen.

Sample Output : 
 '0 is even' 
 '1 is odd' 
 '2 is even'

7.Write a javascript program to enter any number and print all factors of the number.

Advanced

Write a javascript function to find the sum of first and last digit of any number, without convert it to string

 firstAndLast(456) ==> 4 + 6 = 11 
 firstAndLast(123) ==> 1 + 3 = 4 
 firstAndLast(197) ==> 1 + 7 = 8

2.Write a javascript program to draw the stars

    * 
   *** 
  ***** 
 ******* 
********* 
 ******* 
  ***** 
   *** 
    *

Write a program that reads a character for playing the game of Rock-Paper-Scissors. If the character entered by the user is not one of 'P', 'R' or 'S', the program keeps on prompting the user to enter a new character.

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