Day 1: Let and Const | 10 Days of JavaScript | HackerRank Solution

Hello coders, today we are going to solve Day 1: Let and Const HackerRank Solution which is a part of 10 Days of JavaScript Series.

Day 1: Let and Const | 10 Days of JavaScript | HackerRank Solution


In this challenge, we practice declaring variables using the let and const keywords. Check out the attached tutorial for more details.


  1. Declare a constant variablePI, and assign it the value Math.PI. You will not pass this challenge unless the variable is declared as a constant and named PI (uppercase).
  2. Read a number, r, denoting the radius of a circle from stdin.
  3. Use PI and r to calculate the area and perimeter of a circle having radius .
  4. Print area as the first line of output and print perimeter as the second line of output.

Input Format

A single integer, r, denoting the radius of a circle.


  • 0 < r <= 100
  • r  is a floating-point number scaled to at most 3 decimal places.

Output Format

Print the following two lines:

  1. On the first line, print the area of the circle having radius r.
  2. On the second line, print the perimeter of the circle having radius r.

Sample Input 0


Sample Output 0


Explanation 0

Given the radius r = 2.6, we calculate the following:

  • area = π * r^2 = 21.237166338267002
  • perimeter = 2 * π * r = 16.336281798666924

We then print area as our first line of output and perimeter as our second line of output.

Solution – Day 1: Let and Const

'use strict';


let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();

function readLine() {
    return inputString[currentLine++];

function main() {
    // Write your code here. Read input using 'readLine()' and print output using 'console.log()'.
    var r = readLine();
    // Print the area of the circle:
    console.log(Math.PI * r * r);
    // Print the perimeter of the circle:
    console.log(2 * Math.PI * r);

    try {    
        // Attempt to redefine the value of constant variable PI
        PI = 0;
        // Attempt to print the value of PI
    } catch(error) {
        console.error("You correctly declared 'PI' as a constant.");

Disclaimer: The above Problem (Let and Const) is generated by Hacker Rank but the Solution is provided by CodingBroz. This tutorial is only for Educational and Learning Purpose.

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