[feat] add math module with sum function

src/index.js

@@ -2,6 +2,8 @@
 export { download } from './general/download'
 // Http
 export { get } from './http/get'
+// Math
+export { sum } from './math/operations.js'
 // Strings
 export { parseURL } from './strings/parseURL'
 export { capitalize, capitalizeList } from './strings/capitalize'

src/math/operations.js

@@ -0,0 +1,12 @@
+/**
+ * Get numbers and return their sum.
+ * @param numbers
+ * @returns {number}
+ */
+export function sum (...numbers) {
+  if (numbers.some(number => typeof number !== 'number')) {
+    throw TypeError('Parameters must be numbers.')
+  }
+
+  return numbers.reduce((a, b) => a + b, 0)
+}

test/test.js

@@ -1,6 +1,16 @@
 const tape = require('tape')
 const utils = require('../dist/utils')
 
+/** Math module tests **/
+
+tape('Operation functions', function (test) {
+  test.equal(utils.sum(1, 1, 2), 4)
+
+  test.throws(() => utils.sum(1, 2, 'hello'))
+
+  test.end()
+})
+
 /** String module tests **/
 
 tape('Capitalize functions', function (test) {