feat(isPrime): add isPrime function (#147)

* WIP: Add isPrime function

* WIP: Review lint error for isPrime function

Author: alexandru-tomescu

src/index.js

@@ -51,6 +51,7 @@ import arrayAverage from './array-average'
 import find from './find'
 import median from './array-median'
 import timeDifference from './timeDifference'
+import isPrime from './is-prime'
 
 export {
   isOdd,
@@ -106,4 +107,5 @@ export {
   arrayAverage,
   median,
   timeDifference,
+  isPrime,
 }

src/is-prime.js

@@ -0,0 +1,17 @@
+export default isPrime
+
+/**
+ * This method tests if a given number is prime
+ *
+ * @param {Number} number - number to be evaluated
+ * @returns {Boolean} - True if number is prime, false otherwise
+ */
+function isPrime(number) {
+  let i
+  for (i = 2; i < number; i++) {
+    if (number % i === 0) {
+      return false
+    }
+  }
+  return number >= 1
+}

test/is-prime.test.js

@@ -0,0 +1,44 @@
+import test from 'ava'
+import {isPrime} from '../src'
+
+test('check negative numbers -> -3', t => {
+    const expected = false;
+    const actual = isPrime(-3);
+
+    t.is(actual, expected);
+});
+
+test('check negative numbers -> -1', t => {
+    const expected = false;
+    const actual = isPrime(-1);
+
+    t.is(actual, expected);
+});
+
+test('check 0', t => {
+    const expected = false;
+    const actual = isPrime(0);
+
+    t.is(actual, expected);
+});
+
+test('check odd number greater than 2 -> 4', t => {
+    const expected = false;
+    const actual = isPrime(4);
+
+    t.is(actual, expected);
+});
+
+test('check prime numbers -> 1', t => {
+    const expected = true;
+    const actual = isPrime(1);
+
+    t.is(actual, expected);
+});
+
+test('check prime numbers -> 3', t => {
+    const expected = true;
+    const actual = isPrime(3);
+
+    t.is(actual, expected);
+});