merge: Upgraded hexToBinary function (TheAlgorithms#910)

* feat: used js object intead of switch

* pref: optimzed the algo with regex & replace method

* feat: add hex validation with test case

* feat: add type validation

* chore: fix grammar mistake

* docs: add binLookup comments

Author: fahimfaisaal

Conversions/HexToBinary.js

@@ -1,34 +1,41 @@
-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 binLookup = (key) => ({
+  0: '0000',
+  1: '0001',
+  2: '0010',
+  3: '0011',
+  4: '0100',
+  5: '0101',
+  6: '0110',
+  7: '0111',
+  8: '1000',
+  9: '1001',
+  a: '1010',
+  b: '1011',
+  c: '1100',
+  d: '1101',
+  e: '1110',
+  f: '1111'
+}[key.toLowerCase()]) // select the binary number by valid hex key with the help javascript object
+
 const hexToBinary = (hexString) => {
+  if (typeof hexString !== 'string') {
+    throw new TypeError('Argument is not a string type')
+  }
+
+  if (/[^\da-f]/gi.test(hexString)) {
+    throw new Error('Argument is not a valid HEX code!')
+  }
   /*
     Function for converting Hex to Binary
 
     1. We convert every hexadecimal bit to 4 binary bits
     2. Conversion goes by searching in the lookup table
+  */
 
-    */
-  const hexLexemes = hexString.split('')
-  return hexLexemes.map(lexeme => binLookup(lexeme)).join('')
+  return hexString.replace(
+    /[0-9a-f]/gi,
+    lexeme => binLookup(lexeme)
+  )
 }
 
 export default hexToBinary

Conversions/test/HexToBinary.test.js

@@ -1,6 +1,18 @@
 import hexToBinary from '../HexToBinary'
 
-describe('hexToBinary', () => {
+describe('Testing hexToBinary', () => {
+  it('expects throw error in invalid types', () => {
+    expect(() => hexToBinary(false)).toThrowError()
+    expect(() => hexToBinary(null)).toThrowError()
+    expect(() => hexToBinary(23464)).toThrowError()
+  })
+
+  it('expects throw error in invalid hex', () => {
+    expect(() => hexToBinary('Hello i am not a valid Hex')).toThrowError()
+    expect(() => hexToBinary('Gf46f')).toThrowError()
+    expect(() => hexToBinary('M')).toThrowError()
+  })
+
   it('expects to return correct hexadecimal value', () => {
     expect(hexToBinary('8')).toBe('1000')
   })