fix: reject non-binary input in BinaryToHex

Invalid digits made hexLookup return undefined, and reversing
the digits turned that into the string "denifednu".

Author: kevin9327

Conversions/BinaryToHex.js

@@ -44,6 +44,14 @@ const hexLookup = (bin) => {
   }
 }
 const binaryToHex = (binaryString) => {
+  if (typeof binaryString !== 'string') {
+    throw new TypeError('Argument is not a string type')
+  }
+
+  if (!/^[01]+$/.test(binaryString)) {
+    throw new Error('Argument is not a valid binary string!')
+  }
+
   /*
   Function for converting Binary to Hex
 

Conversions/test/BinaryToHex.test.js

@@ -18,4 +18,16 @@ describe('BinaryToHex', () => {
       parseInt('1111', 2).toString(16).toUpperCase()
     )
   })
+
+  it('expects to throw for a non-string argument', () => {
+    expect(() => binaryToHex(1000)).toThrowError()
+    expect(() => binaryToHex(null)).toThrowError()
+  })
+
+  it('expects to throw for a non-binary string', () => {
+    expect(() => binaryToHex('2')).toThrowError()
+    expect(() => binaryToHex('1002')).toThrowError()
+    expect(() => binaryToHex('1010 1101')).toThrowError()
+    expect(() => binaryToHex('')).toThrowError()
+  })
 })