feat(dec2bin): Add a decimal to binary function #67

* feat(dec2bin): Add a decimal to binary function #67

* feat(dec2bin): Add decimal to binary function

Closes #69

* Update message for invalid input from String to RangeError

* Update dec2bin to throw RangeError

Author: ArupSen

src/dec2bin.js

@@ -0,0 +1,18 @@
+export default dec2bin
+
+/**
+ * Converts a decimal integer into binary number
+ * Only works for positive integers
+ * Untested for values greater than 32-bit
+ * Floating point numbers truncated to integer
+ *
+ * @param {String} dec - string version of integer
+ * @return {String} - binary version of input as string
+ */
+function dec2bin(dec) {
+  if (parseInt(dec, 10) < 0) {
+    throw new RangeError('Input must be a positive integer')
+  } else {
+    return parseInt(dec, 10).toString(2)
+  }
+}

src/index.js

@@ -19,6 +19,7 @@ import divide from './divide'
 import multiply from './multiply'
 import square from './square'
 import sum from './sum'
+import dec2bin from './dec2bin'
 
 export {
   flatten,
@@ -42,4 +43,5 @@ export {
   multiply,
   square,
   sum,
+  dec2bin,
 }

test/dec2bin.test.js

@@ -0,0 +1,26 @@
+import test from 'ava'
+import {dec2bin} from '../src'
+
+test('string is not a number', t => {
+  const original = 'five'
+  const expected = 'NaN'
+  const actual = dec2bin(original)
+  t.deepEqual(actual, expected)
+})
+
+test('throws error if number is less than zero', t => {
+  const original = '-123'
+  //const actual = dec2bin(original)
+  const error = t.throws(() => {
+    dec2bin(original)
+  },RangeError)
+  t.is(error.message, 'Input must be a positive integer')
+})
+
+test('outputs binary version as string', t => {
+  const original = '1234'
+  const expected = '10011010010'
+  const actual = dec2bin(original)
+  t.deepEqual(actual, expected)
+})
+