fix: factorial function (TheAlgorithms#1093)

Author: itsAkshayDubey

Maths/Factorial.js

@@ -19,18 +19,18 @@ const calcRange = (num) => {
 
 const calcFactorial = (num) => {
  if (num === 0) {
- return 'The factorial of 0 is 1.'
+ return 1
  }
  if (num < 0) {
- return 'Sorry, factorial does not exist for negative numbers.'
+ throw Error('Sorry, factorial does not exist for negative numbers.')
  }
  if (!num) {
- return 'Sorry, factorial does not exist for null or undefined numbers.'
+ throw Error('Sorry, factorial does not exist for null or undefined numbers.')
  }
  if (num > 0) {
  const range = calcRange(num)
  const factorial = range.reduce((a, c) => a * c, 1)
- return `The factorial of ${num} is ${factorial}`
+ return factorial
  }
 }
 

Maths/test/Factorial.test.js

@@ -2,30 +2,20 @@ import { calcFactorial } from '../Factorial'
 
 describe('calcFactorial', () => {
  it('should return a statement for value "0"', () => {
- expect(calcFactorial(0)).toBe('The factorial of 0 is 1.')
+ expect(calcFactorial(0)).toBe(1)
  })
 
- it('should return a statement for "null" and "undefined"', () => {
- const nullFactorial = calcFactorial(null)
- const undefinedFactorial = calcFactorial(undefined)
-
- expect(nullFactorial).toBe(
- 'Sorry, factorial does not exist for null or undefined numbers.'
- )
- expect(undefinedFactorial).toBe(
- 'Sorry, factorial does not exist for null or undefined numbers.'
- )
+ it('should throw error for "null" and "undefined"', () => {
+ expect(() => { calcFactorial(null) }).toThrow(Error)
+ expect(() => { calcFactorial(undefined) }).toThrow(Error)
  })
 
- it('should not support negative numbers', () => {
- const negativeFactorial = calcFactorial(-5)
- expect(negativeFactorial).toBe(
- 'Sorry, factorial does not exist for negative numbers.'
- )
+ it('should throw error for negative numbers', () => {
+ expect(() => { calcFactorial(-1) }).toThrow(Error)
  })
 
  it('should return the factorial of a positive number', () => {
  const positiveFactorial = calcFactorial(3)
- expect(positiveFactorial).toBe('The factorial of 3 is 6')
+ expect(positiveFactorial).toBe(6)
  })
 })