merge: Add binary to decimal test file and convert function to es6 model. (TheAlgorithms#806)

* Added Hex to Binary conversion

* Add Binary to decimal test

* Fix Style

Author: ddhira123

Conversions/BinaryToDecimal.js

@@ -1,14 +1,8 @@
-export const binaryToDecimal = (binaryString) => {
+export default function binaryToDecimal (binaryString) {
   let decimalNumber = 0
   const binaryDigits = binaryString.split('').reverse() // Splits the binary number into reversed single digits
   binaryDigits.forEach((binaryDigit, index) => {
     decimalNumber += binaryDigit * (Math.pow(2, index)) // Summation of all the decimal converted digits
   })
   return decimalNumber
 }
-
-// > binaryToDecimal('111001')
-// 57
-
-// > binaryToDecimal('101')
-// 5

Conversions/HexToBinary.js

@@ -0,0 +1,37 @@
+const binLookup = (c) => {
+  switch (c.toLowerCase()) {
+    case '0': return '0000'
+    case '1': return '0001'
+    case '2': return '0010'
+    case '3': return '0011'
+    case '4': return '0100'
+    case '5': return '0101'
+    case '6': return '0110'
+    case '7': return '0111'
+    case '8': return '1000'
+    case '9': return '1001'
+    case 'a': return '1010'
+    case 'b': return '1011'
+    case 'c': return '1100'
+    case 'd': return '1101'
+    case 'e': return '1110'
+    case 'f': return '1111'
+    default: return ''
+  }
+}
+const hexToBinary = (hexString) => {
+  /*
+    Function for convertung Hex to Binary
+
+    1. We convert every hexadecimal bit to 4 binary bits
+    2. Conversion goes by searching in the lookup table
+
+    */
+
+  let result = ''
+  hexString = hexString.split('')
+  hexString.forEach(c => { result += binLookup(c) })
+  return result
+}
+
+export default hexToBinary

Conversions/test/BinaryToDecimal.test.js

@@ -0,0 +1,15 @@
+import binaryToDecimal from '../BinaryToDecimal'
+
+describe('BinaryToDecimal', () => {
+  it('expects to return correct decimal value', () => {
+    expect(binaryToDecimal('1000')).toBe(8)
+  })
+
+  it('expects to return correct hexadecimal value for more than one hex digit', () => {
+    expect(binaryToDecimal('01101000')).toBe(104)
+  })
+
+  it('expects to return correct hexadecimal value for padding-required binary', () => {
+    expect(binaryToDecimal('1000101')).toBe(69)
+  })
+})

Conversions/test/HexToBinary.test.js

@@ -0,0 +1,19 @@
+import hexToBinary from '../HexToBinary'
+
+describe('hexToBinary', () => {
+  it('expects to return correct hexadecimal value', () => {
+    expect(hexToBinary('8')).toBe('1000')
+  })
+
+  it('expects to return correct binary value for more than one hex digit', () => {
+    expect(hexToBinary('EA')).toBe('11101010')
+  })
+
+  it('expects to test its robustness as it should be case-insensitive', () => {
+    expect(hexToBinary('4d')).toBe('01001101')
+  })
+
+  it('expects to return correct hexadecimal value, matching (num).toString(2)', () => {
+    expect(hexToBinary('F')).toBe(parseInt('F', 16).toString(2))
+  })
+})