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Hackernoon logoJavaScript Practical Coding Challenges For Beginners by@codeguppy

JavaScript Practical Coding Challenges For Beginners

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@codeguppyCodeGuppy

Teaching kids to code at codeguppy.com

Hello JavaScript code newbie! In this article I'm proposing you a series of coding challenges that will help you practice the basic language constructs and algorithms.

These coding challenges are intended for beginners, therefore the proposed solutions are implemented using only simple and classical programming elements. Each solution is accompanied by an online link that helps you quickly run it in a code playground at codeguppy.com

If you have time, we recommend you to solve the challenges on your own and then compare your solution to the provided solution. If time is limited, just browse through the solutions!

Note: The code is making use of the codeguppy specific function println() to print the results. If you want to run these solutions outside codeguppy.com, just replace println() with console.log() then run them using your browser console tool or node.js.

Coding challenge #1: Print numbers from 1 to 10

https://codeguppy.com/code.html?mrgCtLGA90Ozr0Otrs5Z

for(var i = 1; i <= 10; i++)
{
    println(i);
}

Coding challenge #2: Print the odd numbers less than 100

https://codeguppy.com/code.html?eDLA5XPp3bPxP79H2jKT

for(var i = 1; i <= 100; i += 2)
{
    println(i);
}

Coding challenge #3: Print the multiplication table with 7

https://codeguppy.com/code.html?fpnQzIhnGUUmCUZy1fyQ

for(var i = 1; i <= 10; i++)
{
    var row = "7 * " + i + " = " + 7 * i;
    println(row);
}

Coding challenge #4: Print all the multiplication tables with numbers from 1 to 10

https://codeguppy.com/code.html?78aD4mWSCzoNEVxOQ8tI

for(var i = 1; i <= 10; i++)
{
    printTable(i);
    println("");
}

function printTable(n)
{
    for(var i = 1; i <= 10; i++)
    {
        var row = n + " * " + i + " = " + n * i;
        println(row);
    }
}

Coding challenge #5: Calculate the sum of numbers from 1 to 10

https://codeguppy.com/code.html?Vy6u9kki2hXM4YjsbpuN

var sum = 0;

for(var i = 1; i <= 10; i++)
{
    sum += i;
}

println(sum);

Coding challenge #6: Calculate 10!

https://codeguppy.com/code.html?IIuJX4gnXOndNu0VrywA

var prod = 1;

for(var i = 1; i <= 10; i++)
{
    prod *= i;
}

println(prod);

Coding challenge #7: Calculate the sum of odd numbers greater than 10 and less than 30

https://codeguppy.com/code.html?DcOffOyoIArmNZHVNM2u

var sum = 0;

for(var i = 11; i <= 30; i += 2)
{
    sum += i;
}

println(sum);

Coding challenge #8: Create a function that will convert from Celsius to Fahrenheit

https://codeguppy.com/code.html?oI5mWm6QIMRjY1m9XAmI

function celsiusToFahrenheit(n)
{
    return n * 1.8 + 32;
}

var r = celsiusToFahrenheit(20);
println(r);

Coding challenge #9: Create a function that will convert from Fahrenheit to Celsius

https://codeguppy.com/code.html?mhnf8DpPRqqgsBgbJNpz

function fahrenheitToCelsius(n)
{
    return (n - 32) / 1.8;
}

var r = fahrenheitToCelsius(68);
println(r);

Coding challenge #10: Calculate the sum of numbers in an array of numbers

https://codeguppy.com/code.html?TteeVr0aj33ZyCLR685L

function sumArray(ar)
{
    var sum = 0;
    
    for(var i = 0; i < ar.length; i++)
    {
        sum += ar[i];
    }
    
    return sum;
}

var ar = [2, 3, -1, 5, 7, 9, 10, 15, 95];
var sum = sumArray(ar);
println(sum);

Coding challenge #11: Calculate the average of the numbers in an array of numbers

https://codeguppy.com/code.html?7i9sje6FuJsI44cuncLh

function averageArray(ar)
{
    var n = ar.length;
    var sum = 0;
    
    for(var i = 0; i < n; i++)
    {
        sum += ar[i];
    }
    
    return sum / n;
}

var ar = [1, 3, 9, 15, 90];
var avg = averageArray(ar);

println("Average: ", avg);

Coding challenge #12: Create a function that receives an array of numbers and returns an array containing only the positive numbers

Solution 1:

https://codeguppy.com/code.html?0eztj1v6g7iQLzst3Id3

function getPositives(ar)
{
    var ar2 = [];
    
    for(var i = 0; i < ar.length; i++)
    {
        var el = ar[i];
        
        if (el >= 0)
        {
            ar2.push(el);
        }
    }
    
    return ar2;
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var ar2 = getPositives(ar);

println(ar2);

Coding challenge #12: Create a function that receives an array of numbers and returns an array containing only the positive numbers

Solution 2

https://codeguppy.com/code.html?KefrPtrvJeMpQyrB8V2D

function getPositives(ar)
{
    var ar2 = [];
    
    for(var el of ar)
    {
        if (el >= 0)
        {
            ar2.push(el);
        }
    }
    
    return ar2;
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var ar2 = getPositives(ar);

println(ar2);

Coding challenge #12: Create a function that receives an array of numbers and returns an array containing only the positive numbers

Solution 3

https://codeguppy.com/code.html?qJBQubNA7z10n6pjYmB8

function getPositives(ar)
{
    return ar.filter(el => el >= 0);
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var ar2 = getPositives(ar);
println(ar2);

Coding challenge #13: Find the maximum number in an array of numbers

https://codeguppy.com/code.html?THmQGgOMRUj6PSvEV8HD

function findMax(ar)
{
    var max = ar[0];
    
    for(var i = 0; i < ar.length; i++)
    {
        if (ar[i] > max)
        {
            max = ar[i];
        }
    }
    
    return max;
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var max = findMax(ar);
println("Max: ", max);

Coding challenge #14: Print the first 10 Fibonacci numbers without recursion

https://codeguppy.com/code.html?rKOfPxHbVwxNWI2d8orH

var f0 = 0;
println(f0);

var f1 = 1;
println(f1);

for(var i = 2; i < 10; i++)
{
    var fi = f1 + f0;
    println(fi);
    
    f0 = f1;
    f1 = fi;
}

Coding challenge #15: Create a function that will find the nth Fibonacci number using recursion

https://codeguppy.com/code.html?IneuIg9O0rRV8V76omBk

function findFibonacci(n)
{
    if (n == 0)
        return 0;
        
    if (n == 1)
        return 1;
        
    return findFibonacci(n - 1) + findFibonacci(n - 2);
}

var n = findFibonacci(10);
println(n);

Coding challenge #16: Create a function that will return a Boolean specifying if a number is prime

https://codeguppy.com/code.html?fRYsPEc2vcZTbIU8MKku

function isPrime(n)
{
    if (n < 2)
        return false;
        
    if (n == 2)
        return true;
    
    var maxDiv = Math.sqrt(n);
    
    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
    }
    
    return true;
}

println(2, " is prime? ", isPrime(2));
println(3, " is prime? ", isPrime(3));
println(4, " is prime? ", isPrime(4));
println(5, " is prime? ", isPrime(5));
println(9, " is prime? ", isPrime(9));

Coding challenge #17: Calculate the sum of digits of a positive integer number

https://codeguppy.com/code.html?RHA714FYio8gWgmjWYPz

function sumDigits(n)
{
    var s = n.toString();
    var sum = 0;
    
    for(var char of s)
    {
        var digit = parseInt(char);
        sum += digit;
    }
    
    return sum;
}

var sum = sumDigits(1235231);
println("Sum: ", sum);

Coding challenge #18: Print the first 100 prime numbers

https://codeguppy.com/code.html?gnMVeOZXN6VhLekyvui8

printPrimes(100);

// Function prints the first nPrimes numbers
function printPrimes(nPrimes)
{
    var n = 0;
    var i = 2;
    
    while(n < nPrimes)
    {
        if (isPrime(i))
        {
            println(n, " --> ", i);
            n++;
        }
        
        i++;
    }
}


// Returns true if a number is prime
function isPrime(n)
{
    if (n < 2)
        return false;
        
    if (n == 2)
        return true;
    
    var maxDiv = Math.sqrt(n);
    
    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
    }
    
    return true;
}

Coding challenge #19: Create a function that will return in an array the first "nPrimes" prime numbers greater than a particular number "startAt"

https://codeguppy.com/code.html?mTi7EdKrviwIn4bfrmM7

println(getPrimes(10, 100));

function getPrimes(nPrimes, startAt)
{
    var ar = [];
    
    var i = startAt;
    
    while(ar.length < nPrimes)
    {
        if (isPrime(i))
        {
            ar.push(i);
        }
        
        i++;
    }
    
    return ar;
}

// Returns true if a number is prime
function isPrime(n)
{
    if (n < 2)
        return false;
        
    if (n == 2)
        return true;
    
    var maxDiv = Math.sqrt(n);
    
    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
    }
    
    return true;
}

Coding challenge #20: Rotate an array to the left 1 position

https://codeguppy.com/code.html?MRmfvuQdZpHn0k03hITn

var ar = [1, 2, 3];
rotateLeft(ar);
println(ar);

function rotateLeft(ar)
{
    var first = ar.shift();
    ar.push(first);
}

Coding challenge #21: Rotate an array to the right 1 position

https://codeguppy.com/code.html?fHfZqUmkAVUXKtRupmzZ

var ar = [1, 2, 3];
rotateRight(ar);
println(ar);

function rotateRight(ar)
{
    var last = ar.pop();
    ar.unshift(last);
}

Coding challenge #22: Reverse an array

https://codeguppy.com/code.html?GZddBqBVFlqYrsxi3Vbu

var ar = [1, 2, 3];
var ar2 = reverseArray(ar);
println(ar2);

function reverseArray(ar)
{
    var ar2 = [];
    
    for(var i = ar.length - 1; i >= 0; i--)
    {
        ar2.push(ar[i]);
    }
    
    return ar2;
}

Coding challenge #23: Reverse a string

https://codeguppy.com/code.html?pGpyBz0dWlsj7KR3WnFF

var s = reverseString("JavaScript");
println(s);

function reverseString(s)
{
    var s2 = "";
    
    for(var i = s.length - 1; i >= 0; i--)
    {
        var char = s[i];
        s2 += char;
    }
    
    return s2;
}

Coding challenge #24: Create a function that will merge two arrays and return the result as a new array

https://codeguppy.com/code.html?vcTkLxYTAbIflqdUKivc

var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];

var ar = mergeArrays(ar1, ar2);
println(ar);

function mergeArrays(ar1, ar2)
{
   var ar = [];
   
   for(let el of ar1)
   {
       ar.push(el);
   }
   
   for(let el of ar2)
   {
       ar.push(el);
   }
   
   return ar;
}

Coding challenge #25: Create a function that will receive two arrays of numbers as arguments and return an array composed of all the numbers that are either in the first array or second array but not in both

https://codeguppy.com/code.html?Y9gRdgrl6PPt4QxVs7vf

var ar1 = [1, 2, 3, 10, 5, 3, 14];
var ar2 = [1, 4, 5, 6, 14];

var ar = mergeExclusive(ar1, ar2);
println(ar);

function mergeExclusive(ar1, ar2)
{
    var ar = [];
    
    for(let el of ar1)
    {
        if (!ar2.includes(el))
        {
            ar.push(el);
        }
    }
    
    for(let el of ar2)
    {
        if (!ar1.includes(el))
        {
            ar.push(el);
        }
    }
    
    return ar;
}

Coding challenge #26: Create a function that will receive two arrays and will return an array with elements that are in the first array but not in the second

https://codeguppy.com/code.html?bUduoyY6FfwV5nQGdXzH

var ar1 = [1, 2, 3, 10, 5, 3, 14];
var ar2 = [-1, 4, 5, 6, 14];

var ar = mergeLeft(ar1, ar2);
println(ar);

function mergeLeft(ar1, ar2)
{
    var ar = [];
    
    for(let el of ar1)
    {
        if (!ar2.includes(el))
        {
            ar.push(el);
        }
    }

    return ar;
}

Coding challenge #27: Create a function that will receive an array of numbers as argument and will return a new array with distinct elements

Solution 1

https://codeguppy.com/code.html?OkbtP1ZksGHXwqk7Jh3i

var ar = getDistinctElements([1, 2, 3, 6, -1, 2, 9, 7, 10, -1, 100]);
println(ar);

function getDistinctElements(ar)
{
    var ar2 = [];
    
    for(let i = 0; i < ar.length; i++)
    {
        if (!isInArray(ar[i], ar2))
        {
            ar2.push(ar[i]);
        }
    }
    
    return ar2;
}

function isInArray(n, ar)
{
    for(let i = 0; i < ar.length; i++)
    {
        if (ar[i] === n)
            return true;
    }
    
    return false;
}

Coding challenge #27: Create a function that will receive an array of numbers as argument and will return a new array with distinct elements

Solution 2

https://codeguppy.com/code.html?NjGtyQdMP49QiaAkmwpU

var ar = getDistinctElements([1, 2, 3, 6, -1, 2, 9, 7, 10, -1, 100]);
println(ar);

function getDistinctElements(ar)
{
    var ar2 = [];
    
    var lastIndex = ar.length - 1;
    
    for(let i = 0; i <= lastIndex; i++)
    {
        if (!isInArray(ar[i], ar, i + 1, lastIndex))
        {
            ar2.push(ar[i]);
        }
    }
    
    return ar2;
}

function isInArray(n, ar, fromIndex, toIndex)
{
    for(var i = fromIndex; i <= toIndex; i++)
    {
        if (ar[i] === n)
            return true;
    }
    
    return false;
}

Coding challenge #28: Calculate the sum of first 100 prime numbers

https://codeguppy.com/code.html?v0O9sBfnHbCi1StE2TxA

var n = 10;
println("Sum of first ", n, " primes is ", sumPrimes(10));

function sumPrimes(n)
{
    var foundPrimes = 0;
    var i = 2;
    var sum = 0;
    
    while(foundPrimes < n)
    {
        if (isPrime(i))
        {
            foundPrimes++;
            sum += i;
        }
        
        i++;
    }
    
    return sum;
}

// Returns true if number n is prime
function isPrime(n)
{
    if (n < 2)
        return false;
        
    if (n == 2)
        return true;
    
    var maxDiv = Math.sqrt(n);
    
    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i === 0)
        {
            return false;
        }
    }
    
    return true;
}

Coding challenge #29: Print the distance between the first 100 prime numbers

https://codeguppy.com/code.html?xKQEeKYF1LxZhDhwOH7V

printDistances(100);

// Print distances between the first n prime numbers
function printDistances(n)
{
    var lastPrime = 2;
    var i = lastPrime + 1;
    var foundPrimes = 1;
    
    while(foundPrimes < n)
    {
        if (isPrime(i))
        {
            println(i - lastPrime, "\t", i, " - ", lastPrime);

            foundPrimes++;
            lastPrime = i;
        }
        
        i++;
    }
}

// Returns true if number n is prime
function isPrime(n)
{
    if (n < 2)
        return false;
        
    if (n == 2)
        return true;
    
    var maxDiv = Math.sqrt(n);
    
    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i === 0)
        {
            return false;
        }
    }
    
    return true;
}

Coding challenge #30-a: Create a function that will add two positive numbers of indefinite size. The numbers are received as strings and the result should be also provided as string.

Solution 1

https://codeguppy.com/code.html?v5A0QBsdHaiAVA2CPN5y

var n1 = "2909034221912398942349";
var n2 = "1290923909029309499";
var sum = add(n1, n2);

println(n1, "\n", n2, "\n", sum);

function add(sNumber1, sNumber2)
{
    var s = "";
    var carry = 0;
    
    var maxSize = Math.max(sNumber1.length, sNumber2.length);
    
    for(var i = 0; i < maxSize; i++)
    {
        var digit1 = digitFromRight(sNumber1, i);
        var digit2 = digitFromRight(sNumber2, i);
        
        var sum = digit1 + digit2 + carry;
        var digitSum = sum % 10;
        carry = sum >= 10 ? 1 : 0;
        
        s = digitSum.toString() + s;
    }
    
    if (carry > 0)
        s = carry + s;
    
    return s;
}

function digitFromRight(s, digitNo)
{
    if (digitNo >= s.length)
        return 0;
        
    var char = s[ s.length - 1 - digitNo ];
    return parseInt(char);
}

Coding challenge #30-b: Create a function that will add two positive numbers of indefinite size. The numbers are received as strings and the result should be also provided as string.

Solution 2

https://codeguppy.com/code.html?yMQXcPgfrYxuaIxqQmZc

var n1 = "2909034221912398942349";
var n2 = "1290923909029309499";
var sum = add(n1, n2);

println(n1);
println(n2);
println(sum);

function add(sNumber1, sNumber2)
{
    var maxSize = Math.max(sNumber1.length, sNumber2.length);
    
    var s1 = sNumber1.padStart(maxSize, "0");
    var s2 = sNumber2.padStart(maxSize, "0");

    var s = "";
    var carry = 0;
    
    for(var i = maxSize - 1; i >= 0; i--)
    {
        var digit1 = parseInt(s1[i]);
        var digit2 = parseInt(s2[i]);
        
        var sum = digit1 + digit2 + carry;
        var digitSum = sum % 10;
        carry = sum >= 10 ? 1 : 0;
        
        s = digitSum.toString() + s;
    }
    
    if (carry > 0)
        s = carry + s;
    
    return s;
}

Coding challenge #31a. Create a function that will return the number of words in a text

https://codeguppy.com/code.html?r4kwkcWiHfzQZkM1qrX4

// Solution 1

function countWords(text)
{
    var wasSeparator = true;
    var words = 0;
    
    for(var c of text)
    {
        // if current character is separator then advance and
        // set that the previous character was separator
        if (isSeparator(c))
        {
            wasSeparator = true;
            continue;
        }

        // if current character is not separator
        // ... but if previous was separator...
        if (wasSeparator)
        {
            words++;
            wasSeparator = false;
        }
    }
    
    return words;
}

function isSeparator(c)
{
    var separators = [" ", "\t", "\n", "\r", ",", ";", ".", "!", "?"];
    return separators.includes(c);
}

println(countWords(""));
println(countWords("            "));
println(countWords("JavaScript!!!   "));
println(countWords("     JavaScript"));
println(countWords("    JavaScript is cool      "));
println(countWords("I like to learn JavaScript with codeguppy"));

Coding challenge #31b. Create a function that will return the number of words in a text

https://codeguppy.com/code.html?8pdZSfchSXNxBK1f7r7s

// Solution 2

function countWords(text)
{
    var words = 0;
    
    if (text.length > 0 && !isSeparator(text[0]))
        words++;
    
    for(var i = 1; i < text.length; i++)
    {
        var currChr = text[i];
        var prevChr = text[i - 1];
        
        if (!isSeparator(currChr) && isSeparator(prevChr))
        {
            words++;
        }
    }
    
    return words;
}

function isSeparator(c)
{
    var separators = [" ", "\t", "\n", "\r", ",", ";", ".", "!", "?"];
    return separators.includes(c);
}

println(countWords(""));
println(countWords("            "));
println(countWords("JavaScript!!!   "));
println(countWords("     JavaScript"));
println(countWords("    JavaScript is cool      "));
println(countWords("I like to learn JavaScript with codeguppy"));

Coding challenge #32. Create a function that will capitalize the first letter of each word in a text

https://codeguppy.com/code.html?OJoMXT4GKasSfNeX4hjH

println(captializeWords("Create a function that will capitalize the first letter of each word in a text"));

function captializeWords(text)
{
    var text2 = "";
    
    for(var i = 0; i < text.length; i++)
    {
        var currChr = text[i];
        var prevChr = i > 0 ? text[i - 1] : " ";
        
        if (!isSeparator(currChr) && isSeparator(prevChr))
        {
            currChr = currChr.toUpperCase();
        }
        
        text2 += currChr;
    }
    
    return text2;
}

function isSeparator(c)
{
    var separators = [" ", "\t", "\n", "\r", ",", ";", ".", "!", "?"];
    return separators.includes(c);
}

Coding challenge #33. Calculate the sum of numbers received in a comma delimited string

https://codeguppy.com/code.html?QL6H38rpqjGarwCfsbO3

println(sumCSV("1.5, 2.3, 3.1, 4, 5.5, 6, 7, 8, 9, 10.9"));

function sumCSV(s)
{
    var ar = s.split(",");
    
    var sum = 0;
    
    for(var n of ar)
    {
        sum += parseFloat(n);
    }
    
    return sum;
}

Coding challenge #34. Create a function that will return an array with words inside a text

https://codeguppy.com/code.html?IJI0E4OGnkyTZnoszAzf

var text = "Create a function, that will return an array (of string), with the words inside the text";

println(getWords(text));

function getWords(text)
{
    let startWord = -1;
    let ar = [];
    
    for(let i = 0; i <= text.length; i++)
    {
        let c = i < text.length ? text[i] : " ";

        if (!isSeparator(c) && startWord < 0)
        {
            startWord = i;
        }
        
        if (isSeparator(c) && startWord >= 0)
        {
            let word = text.substring(startWord, i);
            ar.push(word);
            
            startWord = -1;
        }
    }

    return ar;
}

function isSeparator(c)
{
    var separators = [" ", "\t", "\n", "\r", ",", ";", ".", "!", "?", "(", ")"];
    return separators.includes(c);
}

Coding challenge #35. Create a function to convert a CSV text to a “bi-dimensional” array

https://codeguppy.com/code.html?5Hqv93WXQ6OOjAYApLGw

var data = "John;Smith;954-000-0000\nMich;Tiger;305-000-0000\nMonique;Vasquez;103-000-0000";

var ar = csvToArray(data);
println(JSON.stringify(ar));

function csvToArray(data)
{
    var arLines = data.split("\n");

    for(var i = 0; i < arLines.length; i++)
    {
        var arLine = arLines[i].split(";");
        arLines[i] = arLine;
    }
    
    return arLines;
}

Coding challenge #36. Create a function that converts a string to an array of characters

https://codeguppy.com/code.html?XCD9vmSQ34HrascysDBL

Coding challenge #36. Create a function that converts a string to an array of characters
https://codeguppy.com/code.html?XCD9vmSQ34HrascysDBL

Coding challenge #37. Create a function that will convert a string in an array containing the ASCII codes of each character

https://codeguppy.com/code.html?suDlTrNYYmCpNJhZpPdB

println(getCharCodes("I like JavaScript"));

function getCharCodes(s)
{
    var ar = [];
    
    for(var i = 0; i < s.length; i++)
    {
        var code = s.charCodeAt(i);
        ar.push(code);
    }
    
    return ar;
}

Coding challenge #38. Create a function that will convert an array containing ASCII codes in a string

https://codeguppy.com/code.html?QGWEPdBEVk4RFGn6UVhP

println(codesToString([73,32,108,105,107,101,32,74,97,118,97,83,99,114,105,112,116]));

function codesToString(ar)
{
    return String.fromCharCode(...ar);
}

Coding challenge #39. Implement the Caesar cypher

https://codeguppy.com/code.html?kextwiVVb9VwhKajJriG

var text = "I LOVE JAVASCRIPT";
var textEnc = encrypt(text, 13);
var textDec = decrypt(textEnc, 13);

println(text);
println(textEnc);
println(textDec);

// Decrypt a message by using the same encrypt function
// ... but using the inverse of the key (e.g. rotate in the other direction)
function decrypt(msg, key)
{
    return encrypt(msg, key * -1);
}

// Function will implement Caesar Cipher to
// encrypt / decrypt the msg by shifting the letters
// of the message acording to the key
function encrypt(msg, key)
{
    var encMsg = "";

    for(var i = 0; i < msg.length; i++)
    {
        var code = msg.charCodeAt(i);

        // Encrypt only letters in 'A' ... 'Z' interval
        if (code >= 65 && code <= 65 + 26 - 1)
        {
            code -= 65;
            code = mod(code + key, 26);
            code += 65;
        }

        encMsg += String.fromCharCode(code);
    }

    return encMsg;
}


// Modulo function: n mod p
function mod(n, p)
{
    if ( n < 0 )
        n = p - Math.abs(n) % p;

    return n % p;
}

Coding challenge #40. Implement the bubble sort algorithm for an array of numbers

https://codeguppy.com/code.html?6bPnKHLhArSPdUPK2mqm

var ar = [23, 1000, 1, -1, 8, 3];
println(ar);
bubbleSort(ar);
println(ar);

function bubbleSort(ar)
{
    var shouldSort = true;
    var length = ar.length;

    while(shouldSort)
    {
        shouldSort = false;
        length--;
        
        for(var i = 0; i < length; i++)
        {
            var a = ar[i];
            if ( a > ar[i+1] )
            {
                ar[i] = ar[i+1];
                ar[i+1] = a;
                shouldSort = true;
            }
        }
    }
}

Coding challenge #41. Create a function to calculate the distance between two points defined by their x, y coordinates

https://codeguppy.com/code.html?mnAuF3BjhDaFwBtDUnI4

println(getDistance(100, 100, 400, 300));

function getDistance(x1, y1, x2, y2)
{
    var l1 = x2 - x1;
    var l2 = y2 - y1;
    
    return Math.sqrt(l1 * l1 + l2 * l2);
}

Coding challenge #42. Create a function that will return a Boolean value indicating if two circles defined by center coordinates and radius are intersecting

https://codeguppy.com/code.html?cTZiewHGAErNUjYRCE6f

println(collisionCircleCircle(200, 200, 100, 300, 300, 50));

function collisionCircleCircle(circle1X, circle1Y, circle1R, circle2X, circle2Y, circle2R)
{
    return getDistance(circle1X, circle1Y, circle2X, circle2Y) <= circle1R + circle2R;
}

// Calculate the distance between the two specified points
function getDistance(x1, y1, x2, y2)
{
    var l1 = x2 - x1;
    var l2 = y2 - y1;
    
    return Math.sqrt(l1 * l1 + l2 * l2);
}

Coding challenge 43. Create a function that will receive a bi-dimensional array as argument and a number and will extract as a unidimensional array the column specified by the number

https://codeguppy.com/code.html?b22i9I5CUkFTdHF4Bod8

var ar = [ ["John", 120],
            ["Jane", 115],
            ["Thomas", 123],
            ["Mel", 112],
            ["Charley", 122]
         ];

var numbers = extractCol(ar, 1);
println(numbers);

function extractCol(ar, colNo)
{
    var arCol = [];
    
    for(var i = 0; i < ar.length; i++)
    {
        arCol.push(ar[i][colNo]);
    }
    
    return arCol;
}

Coding challenge #44. Create a function that will convert a string containing a binary number into a number

https://codeguppy.com/code.html?iDykr8pqeuTPgZjVAvWv

println(binaryToNumber("11111111"));

function binaryToNumber(sBinary)
{
    return parseInt(sBinary, 2);
}

Coding challenge #45. Create a function to calculate the sum of all the numbers in a jagged array (array contains numbers or other arrays of numbers on an unlimited number of levels)

https://codeguppy.com/code.html?3gu4jcQRpBQWu2EsJrv0

var ar = [1, 2, [15, [23], [5, 12]], [100]];

println(sumArray(ar));

function sumArray(ar)
{
    var sum = 0;
    
    for(var el of ar)
    {
        if (Array.isArray(el))
        {
            el = sumArray(el);
        }
        
        sum += el;
    }
    
    return sum;
}

Coding challenge #46-a. Find the maximum number in a jagged array of numbers or array of numbers

https://codeguppy.com/code.html?oT5nrxux2yAgIRsuXBSK

// Solution 1

var ar = [2, 4, 10, [12, 4, [100, 99], 4], [3, 2, 99], 0];

var max = findMax(ar);
println("Max  = ", max);

// Use recursion to find the maximum numeric value in an array of arrays
function findMax(ar)
{
    var max = -Infinity;

    // Cycle through all the elements of the array
    for(var i = 0; i < ar.length; i++)
    {
        var el = ar[i];

        // If an element is of type array then invoke the same function
        // to find out the maximum element of that subarray
        if ( Array.isArray(el) )
        {
            el = findMax( el );
        }

        if ( el > max )
        {
            max = el;
        }
    }

    return max;
}

Coding challenge #46-b. Find the maximum number in a jagged array of numbers or array of numbers

https://codeguppy.com/code.html?VvLiW0W3lwnMrbwC9epp

// Solution 2

var ar = [2, 4, 10, [12, 4, [100, 99], 4], [3, 2, 99], 0];

var max = findMax(ar);
println("Max  = ", max);

// Use a stack to find the maximum numeric value in an array of arrays
function findMax(arElements)
{
    var max = -Infinity;

    // This is the stack on which will put the first array and then 
    // all the other sub-arrays that we find as we traverse an array     
    var arrays = [];

    arrays.push(arElements);

    // Loop as long as are arrays added to the stack for processing
    while(arrays.length > 0)
    {
        // Extract an array from the stack
        ar = arrays.pop();
        
        // ... and loop through its elements
        for(var i = 0; i < ar.length; i++)
        {
            var el = ar[i];

            // If an element is of type array, we'll add it to stack
            // to be processed later
            if ( Array.isArray(el) )
            {
                arrays.push(el);
                continue;
            }
            
            if ( el > max )
            {
                max = el;
            }
        }
    }

    return max;
}

Coding challenge #47. Deep copy a jagged array with numbers or other arrays in a new array

https://codeguppy.com/code.html?4eRqha7h7kjOLnDTyf00

var ar1 = [2, 4, 10, [12, 4, [100, 99], 4], [3, 2, 99], 0];
var ar2 = copyArray(ar1);

println(ar2);

function copyArray(ar)
{
    var ar2 = [];
    
    for(var el of ar)
    {
        if (Array.isArray(el))
        {
            el = copyArray(el);
        }
        
        ar2.push(el);
    }
    
    return ar2;
}

Coding challenge #48. Create a function to return the longest word(s) in a string

https://codeguppy.com/code.html?6O219iv12e5UaC30fcbG

var text = "Create a function to return the longest word(s) in a sentance.";

println(getLongestWords(text));

function getLongestWords(text)
{
    var words = getWords(text);
    
    var maxSize = 0;
    var maxPositions = [];
    
    for(var i = 0; i < words.length; i++)
    {
        var currWordSize = words[i].length;
        
        if (currWordSize > maxSize)
        {
            maxSize = currWordSize;
            maxPositions = [ i ];
        }
        else if (currWordSize === maxSize)
        {
            maxPositions.push(i);
        }
    }

    return getElements(words, maxPositions);
}

// Get only the elements from specified positions from the array
function getElements(ar, arPositions)
{
    var arNew = [];
    
    for(var pos of arPositions)
    {
        arNew.push(ar[pos]);
    }
    
    return arNew;
}

// Returns an array with the words from specified text
function getWords(text)
{
    let startWord = -1;
    let ar = [];
    
    for(let i = 0; i <= text.length; i++)
    {
        let c = i < text.length ? text[i] : " ";

        if (!isSeparator(c) && startWord < 0)
        {
            startWord = i;
        }
        
        if (isSeparator(c) && startWord >= 0)
        {
            let word = text.substring(startWord, i);
            ar.push(word);
            
            startWord = -1;
        }
    }

    return ar;
}

function isSeparator(c)
{
    var separators = [" ", "\t", "\n", "\r", ",", ";", ".", "!", "?", "(", ")"];
    return separators.includes(c);
}

Coding challenge #49. Shuffle an array of strings

https://codeguppy.com/code.html?EHvbHKy5uPvSKxsaeqWv

var ar = ["Shuffle", "an", "array", "of", "strings"];

println(shuffleArray(ar));

// Shuffle array implemented using Fisher–Yates shuffle algorithm
function shuffleArray(ar)
{
    for(var i = ar.length - 1; i > 0; i--)
    {
        var j = randomInt(0, i - 1);
        
        var t = ar[i];
        ar[i] = ar[j];
        ar[j] = t;
    }
    
    return ar;
}

// Get a random int between min and max (both included)
function randomInt(min, max) 
{
    return Math.floor(Math.random() * (max - min + 1) ) + min;
}

Coding challenge #50. Create a function that will receive n as argument and return an array of n unique random numbers from 1 to n.

https://codeguppy.com/code.html?GfCrzPkGSPKbvLuf6KyA

println(getRandomNumbers(10));

function getRandomNumbers(n)
{
    var ar = [];
    
    for(var i = 1; i <= n; i++)
    {
        ar.push(i);
    }
    
    shuffleArray(ar);
    
    return ar;
}

// Shuffle array implemented using Fisher–Yates shuffle algorithm
function shuffleArray(ar)
{
    for(var i = ar.length - 1; i > 0; i--)
    {
        var j = randomInt(0, i - 1);
        
        var t = ar[i];
        ar[i] = ar[j];
        ar[j] = t;
    }
    
    return ar;
}

// Get a random int between min and max (both included)
function randomInt(min, max) 
{
    return Math.floor(Math.random() * (max - min + 1) ) + min;
}

Coding challenge #51. Find the frequency of characters inside a string. Return the result as an array of objects. Each object has 2 fields: character and number of occurrences.

https://codeguppy.com/code.html?e8wHQuJmeYCDKml5k07d

var ar = getCharFrequency("Find the frequency of characters inside a string");
println(JSON.stringify(ar));

function getCharFrequency(text)
{
    var ar = [];

    for(var chr of text)
    {
        updateFrequency(ar, chr);
    }
    
    return ar;
}

function updateFrequency(ar, chr)
{
    for(var el of ar)
    {
        if (el.chr === chr)
        {
            el.count++;
        }
    }
    
    ar.push({ chr : chr, count : 1 });
}

Coding challenge #52. Calculate Fibonacci(500) with high precision (all decimals)

https://codeguppy.com/code.html?OD5GDYyCVo4wgTRCXzRU

println(fibonacci(500));

function fibonacci(n)
{
    if (n === 0)
        return "0";

    if (n === 1)
        return "1";

    var n1 = "0";
    var n2 = "1";

    for(var i = 2; i <= n; i++)
    {
        var sum = add(n1, n2);

        n1 = n2;
        n2 = sum;
    }

    return n2;
}

function add(sNumber1, sNumber2)
{
    var maxSize = Math.max(sNumber1.length, sNumber2.length);
    
    var s1 = sNumber1.padStart(maxSize, "0");
    var s2 = sNumber2.padStart(maxSize, "0");

    var s = "";
    var carry = 0;
    
    for(var i = maxSize - 1; i >= 0; i--)
    {
        var digit1 = parseInt(s1[i]);
        var digit2 = parseInt(s2[i]);
        
        var sum = digit1 + digit2 + carry;
        var digitSum = sum % 10;
        carry = sum >= 10 ? 1 : 0;

        s = digitSum.toString() + s;
    }
    
    if (carry > 0)
        s = carry + s;
    
    return s;
}

Coding challenge #53. Calculate 70! with high precision (all digits)

https://codeguppy.com/code.html?m4AfgJmCABGNEvKlUNtM

println(factorial(70));

// Calculate factorial(n) ... using big number calculations
function factorial(n)
{
    var prod = "1";
    
    for(var i = 2; i <= n; i++)
    {
        prod = mult(prod, i.toString());
    }
    
    return prod;
}

// Multiplies sNumber1 * sNumber2
// Each number is provided as string
function mult(sNumber1, sNumber2)
{
    // Calculate partial results according to multiplication algorithm
    var partialResults = [];
    
    for(var i = sNumber2.length - 1; i >= 0; i--)
    {
        var digit = parseInt(sNumber2[i]);
        
        var partialResult = multDigit(sNumber1, digit);
        partialResult += "0".repeat(partialResults.length);
        
        partialResults.push(partialResult);
    }
    
    // Sum partial results to obtain the product
    var sum = "";
    
    for(var r of partialResults)
    {
        sum = add(sum, r);
    }
    
    return sum;
}

// Multiplies number sNumber (as string) with a single digit number
function multDigit(sNumber, digit)
{
    var p = "";
    var carry = 0;
    
    for(var i = sNumber.length - 1; i >= 0; i--)
    {
        var numberDigit = parseInt(sNumber[i]);
        
        var prod = digit * numberDigit + carry;
        var prodDigit = prod % 10;
        carry = Math.floor(prod / 10);
        
        p = prodDigit.toString() + p;
    }
    
    if (carry > 0)
        p = carry + p;
        
    return p;
}

function add(sNumber1, sNumber2)
{
    var maxSize = Math.max(sNumber1.length, sNumber2.length);
    
    var s1 = sNumber1.padStart(maxSize, "0");
    var s2 = sNumber2.padStart(maxSize, "0");

    var s = "";
    var carry = 0;
    
    for(var i = maxSize - 1; i >= 0; i--)
    {
        var digit1 = parseInt(s1[i]);
        var digit2 = parseInt(s2[i]);
        
        var sum = digit1 + digit2 + carry;
        var digitSum = sum % 10;
        carry = sum >= 10 ? 1 : 0;

        s = digitSum.toString() + s;
    }
    
    if (carry > 0)
        s = carry + s;
    
    return s;
}

If you have a github account you can fork the entire repository with these challenges from https://github.com/CodeGuppyPrograms/CodingChallenges

I hope you had fun browsing through these coding challenges. If you like them, and you want more coding challenges for beginners please leave a comment or send a tweet to @codeguppy.

Happy coding!

Previously published at https://github.com/CodeGuppyPrograms/CodingChallenges

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