feat(common): add truncate function with tests (#165)

Author: sosmaniac-FCC

src/index.js

@@ -32,6 +32,7 @@ import dec2bin from './dec2bin'
 import searchAndReplace from './search-and-replace'
 import sqrt from './sqrt'
 import toPower from './to-power'
+import truncate from './truncate'
 import mod from './mod'
 import shallowEqual from './shallow-equal'
 import swapCase from './swap-case'
@@ -94,6 +95,7 @@ export {
   searchAndReplace,
   sqrt,
   toPower,
+  truncate,
   mod,
   shallowEqual,
   swapCase,

src/truncate.js

@@ -0,0 +1,16 @@
+export default truncate
+
+/**
+ * Original Source: https://stackoverflow.com/questions/1301512/truncate-a-string-straight-javascript
+ * This method will perserve a specified amount of starting characters and delete the rest
+ * @param {String} target - the string to truncate
+ * @param {Number} length - the amount of saved characters prior to truncation
+ * @return {String} - the truncated string
+ */
+
+function truncate(target, length) {
+  if (target.length <= length) {
+    return target
+  }
+  return `${target.toString().substring(0, length)}...`
+}

test/truncate.test.js

@@ -0,0 +1,18 @@
+import test from 'ava'
+import {truncate} from '../src'
+
+test('string truncates by the indicated length', t => {
+  const toTrunc = 'This is a long sentence that needs to be truncated'
+  const index = 15
+  const expected = 'This is a long ...'
+  const actual = truncate(toTrunc, index)
+  t.deepEqual(actual, expected)
+})
+
+test('string does not truncate due to its small size', t => {
+  const toTrunc = 'Short phrase'
+  const index = 15
+  const expected = 'Short phrase'
+  const actual = truncate(toTrunc, index)
+  t.deepEqual(actual, expected)
+})