fix: reject non-binary input in BinaryToDecimal

Digits other than 0 and 1 were coerced into the place-value sum,
so binaryToDecimal('2') returned 2 and binaryToDecimal('102')
returned 6.

Author: kevin9327

Conversions/BinaryToDecimal.js

@@ -1,4 +1,12 @@
 export default function binaryToDecimal(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!')
+  }
+
   let decimalNumber = 0
   const binaryDigits = binaryString.split('').reverse() // Splits the binary number into reversed single digits
   binaryDigits.forEach((binaryDigit, index) => {

Conversions/test/BinaryToDecimal.test.js

@@ -12,4 +12,15 @@ describe('BinaryToDecimal', () => {
   it('expects to return correct hexadecimal value for padding-required binary', () => {
     expect(binaryToDecimal('1000101')).toBe(69)
   })
+
+  it('expects to throw for a non-string argument', () => {
+    expect(() => binaryToDecimal(1000)).toThrowError()
+    expect(() => binaryToDecimal(null)).toThrowError()
+  })
+
+  it('expects to throw for a non-binary string', () => {
+    expect(() => binaryToDecimal('2')).toThrowError()
+    expect(() => binaryToDecimal('102')).toThrowError()
+    expect(() => binaryToDecimal('')).toThrowError()
+  })
 })