# JavaScript Math and Numbers - Exercises, Practice, Solution

## JavaScript Math [53 exercises with solution]

[*An editor is available at the bottom of the page to write and execute the scripts.*]

**1. **Write a JavaScript function to convert a number from one base to another. ** **Go to the editor

*Note* : Both bases must be between 2 and 36.

*Test Data* :

console.log(base_convert('E164',16,8));

console.log(base_convert(1000,2,8));

"160544"

"10"

Click me to see the solution

**2. **Write a JavaScript function to convert a binary number to a decimal number. ** **Go to the editor

*Test Data* :

console.log(bin_to_dec('110011'));

console.log(bin_to_dec('100'));

51

4

Click me to see the solution

**3. **Write a JavaScript function to convert a decimal number to binary, hexadecimal or octal number. ** **Go to the editor

*Test Data* :

console.log(dec_to_bho(120,'B'));

console.log(dec_to_bho(120,'H'));

console.log(dec_to_bho(120,'O'));

"1111000"

"78"

"170"

Click me to see the solution

**4. **Write a JavaScript function to generate a random integer. ** **Go to the editor

*Test Data* :

console.log(rand(20,1));

console.log(rand(1,10));

console.log(rand(6));

console.log(rand());

15

5

1

0

Click me to see the solution

**5. ** Write a JavaScript function to format a number up to specified decimal places. Go to the editor

*Test Data* :

console.log(decimals(2.100212, 2));

console.log(decimals(2.100212, 3));

console.log(decimals(2100, 2));

"2.10"

"2.100"

"2100.00"

Click me to see the solution

**6.** Write a JavaScript function to find the highest value in an array. Go to the editor

*Test Data* :

console.log(max([12,34,56,1]));

console.log(max([-12,-34,0,-56,-1]));

56

0

Click me to see the solution

**7. ** Write a JavaScript function to find the lowest value in an array. Go to the editor

*Test Data* :

console.log(min([12,34,56,1]));

console.log(min([-12,-34,0,-56,-1]));

1

-56

Click me to see the solution

**8. ** Write a JavaScript function to get the greatest common divisor (gcd) of two integers. Go to the editor

*Note* :

According to Wikipedia - In mathematics, the greatest common divisor (gcd) of two or more integers, when at least one of them is not zero, is the largest positive integer that divides the numbers without a remainder. For example, the GCD of 8 and 12 is 4.

*Test Data* :

console.log(gcd_two_numbers(12, 13));

console.log(gcd_two_numbers(9, 3));

*Output * :

1

3

Click me to see the solution

**9. ** Write a JavaScript function to find the GCD (greatest common divisor) of more than 2 integers. Go to the editor

*Test Data* :

console.log(gcd_more_than_two_numbers([3,15,27]));

console.log(gcd_more_than_two_numbers([5,10,15,25]));

*Output * :

3

5

Click me to see the solution

**10. ** Write a JavaScript function to get the least common multiple (LCM) of two numbers. Go to the editor

*Note* :

According to Wikipedia - A common multiple is a number that is a multiple of two or more integers. The common multiples of 3 and 4 are 0, 12, 24, .... The least common multiple (LCM) of two numbers is the smallest number (not zero) that is a multiple of both.

*Test Data* :

console.log(lcm_two_numbers(3,15));

console.log(lcm_two_numbers(10,15));

*Output * :

15

30

Click me to see the solution

**11. ** Write a JavaScript function to get the least common multiple (LCM) of more than 2 integers. Go to the editor

*Test Data* :

console.log(lcm_more_than_two_numbers([100,90,80,7]));

console.log(lcm_more_than_two_numbers([5,10,15,25]));

*Output * :

25200

150

Click me to see the solution

**12. ** Write a JavaScript function to find out if a number is a natural number or not. Go to the editor

Note :

Natural numbers are whole numbers from 1 upwards : 1, 2, 3, and so on ...
or from 0 upwards in some area of mathematics: 0, 1, 2, 3 and so on ...

No negative numbers and no fractions.

*Test Data* :

console.log(is_Natural(-15));

console.log(is_Natural(1));

console.log(is_Natural(10.22));

console.log(is_Natural(10/0));

*Output * :

false

true

false

false

Click me to see the solution

**13. **Write a JavaScript function to test if a number is a power of 2. Go to the editor

*Test Data* :

console.log(power_of_2(16));

console.log(power_of_2(18));

console.log(power_of_2(256));

*Output * :

true

false

true

Click me to see the solution

**14. **Write a JavaScript function to round a number to a given decimal places. Go to the editor

*Test Data* :

console.log(precise_round(12.375,2));

console.log(precise_round(12.37499,2));

console.log(precise_round(-10.3079499, 3));

*Output * :

"12.38"

"12.37"

"-10.308"

Click me to see the solution

**15. **Write a JavaScript function to check whether a value is an integer or not. Go to the editor

*Note* : Integer - A number which is not a fraction; a whole number.

*Test Data* :

console.log(is_Int(23));

console.log(is_Int(4e2));

console.log(is_Int(NaN));

console.log(is_Int(23.75));

console.log(is_Int(-23));

*Output * :

true

true

false

false

true

Click me to see the solution

**16. **Write a JavaScript function to check to check whether a variable is numeric or not. Go to the editor

*Test Data* :

console.log(is_Numeric(12));

console.log(is_Numeric('abcd'));

console.log(is_Numeric('12'));

console.log(is_Numeric(' '));

console.log(is_Numeric(1.20));

console.log(is_Numeric(-200));

*Output * :

true

false

true

false

true

true

Click me to see the solution

**17. **Write a JavaScript function to calculate the sum of values in an array. Go to the editor

*Test Data* :

console.log(sum([1,2,3]));

console.log(sum([100,-200,3]));

console.log(sum([1,2,'a',3]));

*Output * :

6

-97

6

Click me to see the solution

**18. **Write a JavaScript function to calculate the product of values in an array. Go to the editor

*Test Data* :

console.log(product([1,2,3]));

console.log(product([100,-200,3]));

console.log(product([1,2,'a',3]));

*Output * :

6

-60000

6

Click me to see the solution

**19. ** Create a Pythagorean function in JavaScript. Go to the editor

*Note* : The Pythagorean Theorem tells us that the relationship in every right triangle is : c^{2} = a^{2} + b^{2}, where c is the hypotenuse and a, b are two legs of the triangle.

*Test Data* :

console.log(pythagorean_theorem(2, 4));

console.log(pythagorean_theorem(3, 4));

*Output * :

4.47213595499958

5

Click me to see the solution

**20. ** Write a JavaScript program to evaluate binomial coefficients. Go to the editor

*Note* :

Binomial coefficient : According to Wikipedia - In mathematics, binomial coefficients are a family of positive integers that occur as coefficients in the binomial theorem. They are indexed by two nonnegative integers; the binomial coefficient indexed by n and k. Under suitable circumstances the value of the coefficient is given by the expression :

Arranging binomial coefficients into rows for successive values of n, and in which k ranges from 0 to n, gives a triangular array called Pascal's triangle.

*Test Data* :

console.log(binomial(8,3));

console.log(binomial(10,2));

*Output * :

56

45

**21.** Write a JavaScript function that Convert an integer into a Roman Numeral in javaScript. Go to the editor

**22.** Write a JavaScript function that Convert Roman Numeral to Integer. Go to the editor

Click me to see the solution

**23. ** Write a JavaScript function to create a UUID identifier. Go to the editor

*Note* :

According to Wikipedia - A universally unique identifier (UUID) is an identifier standard used in software construction. A UUID is simply a 128-bit value. The meaning of each bit is defined by any of several variants. For human-readable display, many systems use a canonical format using hexadecimal text with inserted hyphen characters. For example : de305d54-75b4-431b-adb2-eb6b9e546014

**24. ** Write a JavaScript function to round a number to a specified number of digits and strip extra zeros (if any). Go to the editor

Test Data :

var a = -4.55555;

console.log(result);

-4.5556

var a = 5.0001000;

console.log(result);

5.0001

Click me to see the solution

**25. **Write a JavaScript function to make currency math (add, subtract, multiply, division etc.). Go to the editor

Test Data :

n1 = '$40.24', n2 = '$21.57';

Click me to see the solution

**26. **Write a JavaScript function to calculate the nth root of a number. Go to the editor

Test Data :

console.log(nthroot(64, 2));

8

console.log(nthroot(64, -2));

0.125

Click me to see the solution

**27. **Write a JavaScript function to calculate degrees between 2 points with inverse Y axis. Go to the editor

Test Data :

console.log(pointDirection(1, 0, 12, 0));

0

console.log(pointDirection(1, 0, 1, 10));

90

Click me to see the solution

**28. **Write a JavaScript function to round up an integer value to the next multiple of 5. Go to the editor

Test Data :

console.log(int_round5(32));

35

console.log(int_round5(137));

140

Click me to see the solution

**29. **Write a JavaScript function to convert a positive number to negative number. Go to the editor

Test Data :

console.log(pos_to_neg(15));

-15

Click me to see the solution

**30. **Write a JavaScript function to cast a square root of a number to an integer. Go to the editor

Test Data :

console.log(sqrt_to_int(17));

4

Click me to see the solution

**31. **Write a JavaScript function to get the highest number from three different numbers. Go to the editor

Test Data :

console.log(highest_of_three(-5, 4, 2));

4

Click me to see the solution

**32. **Write a JavaScript function to calculate the percentage (%) of a number. Go to the editor

Test Data :

console.log(percentage(1000, 47.12));

471.2

Click me to see the solution

**33. **Write a JavaScript function to convert degrees to radians. Go to the editor

Test Data :

console.log(degrees_to_radians(45));

0.7853981633974483

Click me to see the solution

**34. **Write a JavaScript function to convert radians to degrees. Go to the editor

Test Data :

console.log(radians_to_degrees(0.7853981633974483));

45

Click me to see the solution

**35. **Write a JavaScript function for the Pythagorean theorem. Go to the editor

According to Wikipedia : In mathematics, the Pythagorean theorem, also known as Pythagoras' theorem, is a relation in Euclidean geometry among the three sides of a right triangle. It states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides. The theorem can be written as an equation relating the lengths of the sides a, b and c, often called the "Pythagorean equation".

Test Data :

console.log(pythagorean(4, 3));

5

Click me to see the solution

**36. **Write a JavaScript function which will return values that are powers of two. Go to the editor

Test Data :

console.log(isPower_of_two(64));

true

console.log(isPower_of_two(94));

false

Click me to see the solution

**37. **Write a JavaScript function to limit a value inside a certain range. Go to the editor

Note : If the value is higher than max it will return max. and if the value is smaller than min it will return the min.

Test Data :

console.log(value_limit(7, 1, 12));

7

console.log(value_limit(-7, 0, 12));

0

console.log(value_limit(15, 0, 12));

12

Click me to see the solution

**38. **Write a JavaScript function to check if a number is a whole number or has a decimal place. Go to the editor

Note : Whole Numbers are simply the numbers 0, 1, 2, 3, 4, 5, ... (and so on). No Fractions!

Test Data :

console.log(number_test(25.66));

"Number has a decimal place."

console.log(number_test(10));

"It is a whole number."

Click me to see the solution

**39. **Write a JavaScript function to print an integer with commas as thousands separators. Go to the editor

Test Data :

console.log(thousands_separators(1000));

"1,000"

console.log(thousands_separators(10000.23));

"10,000.23"

console.log(thousands_separators(100000));

"100,000"

Click me to see the solution

**40. **Write a JavaScript function to create random background color. Go to the editor

Click me to see the solution

**41. **Write a JavaScript function to count the digits of an integer. Go to the editor

Click me to see the solution

**42. **Write a JavaScript function to calculate the combination of n and r. Go to the editor

The formula is : n!/(r!*(n - r)!).

*Test Data* :

console.log(combinations(6, 2));

15

console.log(combinations(5, 3));

10

Click me to see the solution

**43. **Write a JavaScript function to get all prime numbers from 0 to a specified number. Go to the editor

*Test Data* :

console.log(primeFactorsTo(5));

[2, 3, 5]

console.log(primeFactorsTo(15));

[2, 3, 5, 7, 11, 13]

Click me to see the solution

**44. **Write a JavaScript function to show the first twenty Hamming numbers. Go to the editor

Hamming Numbers are numbers whose only prime factors are 2, 3 and 5.

Click me to see the solution

**45. **Write a JavaScript function to subtract elements from one another in an array. Go to the editor

Click me to see the solution

**46. **Write a JavaScript function to calculate the divisor and modulus of two integers. Go to the editor

Click me to see the solution

**47. **Write a JavaScript function to calculate the extended Euclid Algorithm or extended GCD. Go to the editor

In mathematics, the Euclidean algorithm[a], or Euclid's algorithm, is an efficient method for computing the greatest common divisor (GCD) of two numbers, the largest number that divides both of them without leaving a remainder. It is named after the ancient Greek mathematician Euclid, who first described it in Euclid's Elements. It is an example of an algorithm, a step-by-step procedure for performing a calculation according to well-defined rules, and is one of the oldest algorithms in common use. It can be used to reduce fractions to their simplest form, and is a part of many other number-theoretic and cryptographic calculations.

Click me to see the solution

**48. **Write a JavaScript function to calculate the falling factorial of a number. Go to the editor

Let x be a real number (but usually an integer).

Let k be a positive integer.

Then x to the (power of) k falling is :

This is called the kth falling factorial power of x.

Click me to see the solution

**49. **Write a JavaScript function to calculate Lanczos approximation gamma. Go to the editor

In mathematics, the Lanczos approximation is a method for computing the Gamma function numerically, published by Cornelius Lanczos in 1964. It is a practical alternative to the more popular Stirling's approximation for calculating the Gamma function with fixed precision.

Click me to see the solution

**50. **Write a JavaScript program to add two complex numbers. Go to the editor

A complex number is a number that can be expressed in the form a + bi, where a and b are real numbers and i is the imaginary unit, that satisfies the equation i^{2} = −1. In this expression, a is the real part and b is the imaginary part of the complex number.

Click me to see the solution

**51. **Write a JavaScript program to subtract two complex numbers. Go to the editor

Click me to see the solution

**52. **Write a JavaScript program to multiply two complex numbers. Go to the editor

Click me to see the solution

**53. **Write a JavaScript program to divide two complex numbers. Go to the editor

Click me to see the solution

**More to Come ! **

* To run the code mouse over on Result panel and click on 'RERUN' button.*

**Live Demo: **

See the Pen javascript-common-editor by w3resource (@w3resource) on CodePen.

## JavaScript: Tips of the Day

**Applies a function against an accumulator and each key in the object (from left to right)**

Example:

const transform = (obj, fn, acc) => Object.keys(obj).reduce((a, k) => fn(a, obj[k], k, obj), acc); console.log(transform( { a: 1, b: 2, c: 1 }, (r, v, k) => { (r[v] || (r[v] = [])).push(k); return r; }, {} )); // { '1': ['a', 'c'], '2': ['b'] }

Output:

[object Object] { 1: ["a", "c"], 2: ["b"] }

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