diff --git a/lib/cache_stream.js b/lib/cache_stream.js
index 640d9412..91e65124 100644
--- a/lib/cache_stream.js
+++ b/lib/cache_stream.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var Transform = require('stream').Transform;
+const { Transform } = require('stream');
 
 function CacheStream() {
   Transform.call(this);
@@ -11,7 +11,7 @@ function CacheStream() {
 require('util').inherits(CacheStream, Transform);
 
 CacheStream.prototype._transform = function(chunk, enc, callback) {
-  var buf = chunk instanceof Buffer ? chunk : Buffer.from(chunk, enc);
+  const buf = chunk instanceof Buffer ? chunk : Buffer.from(chunk, enc);
 
   this._cache.push(buf);
   this.push(buf);
diff --git a/lib/camel_case_keys.js b/lib/camel_case_keys.js
index 40b0badf..6008b910 100644
--- a/lib/camel_case_keys.js
+++ b/lib/camel_case_keys.js
@@ -1,8 +1,8 @@
 'use strict';
 
-var camelCase = require('camel-case');
+const camelCase = require('camel-case');
 
-var rPrefixUnderscore = /^(_+)/;
+const rPrefixUnderscore = /^(_+)/;
 
 function getter(key) {
   return function() {
@@ -19,17 +19,17 @@ function setter(key) {
 function camelCaseKeys(obj) {
   if (typeof obj !== 'object') throw new TypeError('obj must be an object!');
 
-  var keys = Object.keys(obj);
-  var result = {};
+  const keys = Object.keys(obj);
+  const result = {};
 
-  for (var i = 0, len = keys.length; i < len; i++) {
-    var key = keys[i];
-    var value = obj[key];
-    var match = key.match(rPrefixUnderscore);
-    var newKey;
+  for (let i = 0, len = keys.length; i < len; i++) {
+    const key = keys[i];
+    const value = obj[key];
+    const match = key.match(rPrefixUnderscore);
+    let newKey;
 
     if (match) {
-      var underscore = match[1];
+      const underscore = match[1];
       newKey = underscore + camelCase(key.substring(underscore.length));
     } else {
       newKey = camelCase(key);
@@ -39,8 +39,12 @@ function camelCaseKeys(obj) {
       result[key] = value;
     } else {
       result[newKey] = value;
-      result.__defineGetter__(key, getter(newKey));
-      result.__defineSetter__(key, setter(newKey));
+      Object.defineProperty(result, key, {
+        get: getter(newKey),
+        set: setter(newKey),
+        configurable: true,
+        enumerable: true
+      });
     }
   }
 
diff --git a/lib/escape_diacritic.js b/lib/escape_diacritic.js
index 2b39d827..5e94465d 100644
--- a/lib/escape_diacritic.js
+++ b/lib/escape_diacritic.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var defaultDiacriticsRemovalap = [
+const defaultDiacriticsRemovalap = [
   {'base': 'A', 'letters': '\u0041\u24B6\uFF21\u00C0\u00C1\u00C2\u1EA6\u1EA4\u1EAA\u1EA8\u00C3\u0100\u0102\u1EB0\u1EAE\u1EB4\u1EB2\u0226\u01E0\u00C4\u01DE\u1EA2\u00C5\u01FA\u01CD\u0200\u0202\u1EA0\u1EAC\u1EB6\u1E00\u0104\u023A\u2C6F'},
   {'base': 'AA', 'letters': '\uA732'},
   {'base': 'AE', 'letters': '\u00C6\u01FC\u01E2'},
@@ -89,12 +89,12 @@ var defaultDiacriticsRemovalap = [
   {'base': 'z', 'letters': '\u007A\u24E9\uFF5A\u017A\u1E91\u017C\u017E\u1E93\u1E95\u01B6\u0225\u0240\u2C6C\uA763'}
 ];
 
-var diacriticsMap = {};
+const diacriticsMap = {};
 
-for (var i = 0; i < defaultDiacriticsRemovalap.length; i++) {
-  var letters = defaultDiacriticsRemovalap[i].letters.split('');
+for (let i = 0; i < defaultDiacriticsRemovalap.length; i++) {
+  const letters = defaultDiacriticsRemovalap[i].letters.split('');
 
-  for (var j = 0; j < letters.length; j++) {
+  for (let j = 0; j < letters.length; j++) {
     diacriticsMap[letters[j]] = defaultDiacriticsRemovalap[i].base;
   }
 }
@@ -104,9 +104,7 @@ function escapeDiacritic(str) {
 
   // http://stackoverflow.com/a/18391901
   // eslint-disable-next-line no-control-regex
-  return str.replace(/[^\u0000-\u007E]/g, function(a) {
-    return diacriticsMap[a] || a;
-  });
+  return str.replace(/[^\u0000-\u007E]/g, a => diacriticsMap[a] || a);
 }
 
 module.exports = escapeDiacritic;
diff --git a/lib/escape_html.js b/lib/escape_html.js
index f094eb66..8c51211b 100644
--- a/lib/escape_html.js
+++ b/lib/escape_html.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var htmlEntityMap = {
+const htmlEntityMap = {
   '&': '&amp;',
   '<': '&lt;',
   '>': '&gt;',
@@ -13,9 +13,7 @@ function escapeHTML(str) {
   if (typeof str !== 'string') throw new TypeError('str must be a string!');
 
   // http://stackoverflow.com/a/12034334
-  return str.replace(/[&<>"'/]/g, function(a) {
-    return htmlEntityMap[a];
-  });
+  return str.replace(/[&<>"'/]/g, a => htmlEntityMap[a]);
 }
 
 module.exports = escapeHTML;
diff --git a/lib/hash.js b/lib/hash.js
index 4a7197e6..3112a588 100644
--- a/lib/hash.js
+++ b/lib/hash.js
@@ -1,9 +1,9 @@
 'use strict';
 
-var Transform = require('stream').Transform;
-var crypto = require('crypto');
+const { Transform } = require('stream');
+const crypto = require('crypto');
 
-var ALGORITHM = 'sha1';
+const ALGORITHM = 'sha1';
 
 function HashStream() {
   Transform.call(this);
@@ -23,8 +23,8 @@ HashStream.prototype._flush = function(callback) {
   callback();
 };
 
-exports.hash = function(content) {
-  var hash = crypto.createHash(ALGORITHM);
+exports.hash = content => {
+  const hash = crypto.createHash(ALGORITHM);
   hash.update(content);
   return hash.digest();
 };
diff --git a/lib/highlight.js b/lib/highlight.js
index f97d73fd..42fa2aa9 100644
--- a/lib/highlight.js
+++ b/lib/highlight.js
@@ -1,72 +1,71 @@
 'use strict';
 
-var hljs = require('highlight.js/lib/highlight');
-var Entities = require('html-entities').XmlEntities;
-var entities = new Entities();
-var alias = require('../highlight_alias.json');
+const hljs = require('highlight.js/lib/highlight');
+const Entities = require('html-entities').XmlEntities;
+const entities = new Entities();
+const alias = require('../highlight_alias.json');
 
-function highlightUtil(str, options) {
+function highlightUtil(str, options = {}) {
   if (typeof str !== 'string') throw new TypeError('str must be a string!');
-  options = options || {};
 
-  var useHljs = options.hasOwnProperty('hljs') ? options.hljs : false;
-  var gutter = options.hasOwnProperty('gutter') ? options.gutter : true;
-  var wrap = options.hasOwnProperty('wrap') ? options.wrap : true;
-  var firstLine = options.hasOwnProperty('firstLine') ? +options.firstLine : 1;
-  var caption = options.caption;
-  var mark = options.hasOwnProperty('mark') ? options.mark : [];
-  var tab = options.tab;
+  const useHljs = options.hasOwnProperty('hljs') ? options.hljs : false;
+  const {
+    gutter = true,
+    firstLine = 1,
+    caption,
+    mark = [],
+    tab
+  } = options;
+  let { wrap = true } = options;
 
   hljs.configure({ classPrefix: useHljs ? 'hljs-' : ''});
 
-  var data = highlight(str, options);
+  const data = highlight(str, options);
 
   if (useHljs && !gutter) wrap = false;
 
-  var before = useHljs ? '<pre><code class="hljs ' + options.lang + '">' : '<pre>';
-  var after = useHljs ? '</code></pre>' : '</pre>';
+  const before = useHljs ? `<pre><code class="hljs ${options.lang}">` : '<pre>';
+  const after = useHljs ? '</code></pre>' : '</pre>';
 
   if (!wrap) return useHljs ? before + data.value + after : data.value;
 
-  var lines = data.value.split('\n');
-  var numbers = '';
-  var content = '';
-  var result = '';
-  var line;
+  const lines = data.value.split('\n');
+  let numbers = '';
+  let content = '';
 
-  for (var i = 0, len = lines.length; i < len; i++) {
-    line = lines[i];
+  for (let i = 0, len = lines.length; i < len; i++) {
+    let line = lines[i];
     if (tab) line = replaceTabs(line, tab);
-    numbers += '<span class="line">' + (firstLine + i) + '</span><br>';
+    numbers += `<span class="line">${firstLine + i}</span><br>`;
     content += formatLine(line, firstLine + i, mark, options);
   }
 
-  result += '<figure class="highlight' + (data.language ? ' ' + data.language : '') + '">';
+  let result = `<figure class="highlight${data.language ? ` ${data.language}` : ''}">`;
 
   if (caption) {
-    result += '<figcaption>' + caption + '</figcaption>';
+    result += `<figcaption>${caption}</figcaption>`;
   }
 
   result += '<table><tr>';
 
   if (gutter) {
-    result += '<td class="gutter"><pre>' + numbers + '</pre></td>';
+    result += `<td class="gutter"><pre>${numbers}</pre></td>`;
   }
 
-  result += '<td class="code">' + before + content + after + '</td>';
+  result += `<td class="code">${before}${content}${after}</td>`;
   result += '</tr></table></figure>';
 
   return result;
 }
 
 function formatLine(line, lineno, marked, options) {
-  var useHljs = options.hljs || false;
-  var res = useHljs ? '' : '<span class="line';
-  if (marked.indexOf(lineno) !== -1) {
+  const useHljs = options.hljs || false;
+  let res = useHljs ? '' : '<span class="line';
+  if (marked.includes(lineno)) {
     // Handle marked lines.
-    res += useHljs ? '<mark>' + line + '</mark>' : ' marked">' + line + '</span>';
+    res += useHljs ? `<mark>${line}</mark>` : ` marked">${line}</span>`;
   } else {
-    res += useHljs ? line : '">' + line + '</span>';
+    res += useHljs ? line : `">${line}</span>`;
   }
 
   res += '<br>';
@@ -78,10 +77,10 @@ function encodePlainString(str) {
 }
 
 function replaceTabs(str, tab) {
-  return str.replace(/^\t+/, function(match) {
-    var result = '';
+  return str.replace(/^\t+/, match => {
+    let result = '';
 
-    for (var i = 0, len = match.length; i < len; i++) {
+    for (let i = 0, len = match.length; i < len; i++) {
       result += tab;
     }
 
@@ -90,7 +89,7 @@ function replaceTabs(str, tab) {
 }
 
 function loadLanguage(lang) {
-  hljs.registerLanguage(lang, require('highlight.js/lib/languages/' + lang));
+  hljs.registerLanguage(lang, require(`highlight.js/lib/languages/${lang}`));
 }
 
 function tryLanguage(lang) {
@@ -102,29 +101,25 @@ function tryLanguage(lang) {
 }
 
 function loadAllLanguages() {
-  alias.languages.filter(function(lang) {
-    return !hljs.getLanguage(lang);
-  }).forEach(loadLanguage);
+  alias.languages.filter(lang => !hljs.getLanguage(lang)).forEach(loadLanguage);
 }
 
 function highlight(str, options) {
-  var lang = options.lang;
-  var autoDetect = options.hasOwnProperty('autoDetect') ? options.autoDetect : false;
+  let { lang } = options;
+  const { autoDetect = false } = options;
 
   if (!lang && autoDetect) {
     loadAllLanguages();
-    lang = (function() {
-      var result = hljs.highlightAuto(str);
-      if (result.relevance > 0 && result.language) return result.language;
+    const result = hljs.highlightAuto(str);
+    if (result.relevance > 0 && result.language) lang = result.language;
 
-    }());
   }
 
   if (!lang) {
     lang = 'plain';
   }
 
-  var result = {
+  const result = {
     value: encodePlainString(str),
     language: lang.toLowerCase()
   };
@@ -145,11 +140,11 @@ function highlight(str, options) {
 
 function tryHighlight(str, lang) {
   try {
-    var matching = str.match(/(\r?\n)/);
-    var separator = matching ? matching[1] : '';
-    var lines = matching ? str.split(separator) : [str];
-    var result = hljs.highlight(lang, lines.shift());
-    var html = result.value;
+    const matching = str.match(/(\r?\n)/);
+    const separator = matching ? matching[1] : '';
+    const lines = matching ? str.split(separator) : [str];
+    let result = hljs.highlight(lang, lines.shift());
+    let html = result.value;
     while (lines.length > 0) {
       result = hljs.highlight(lang, lines.shift(), false, result.top);
       html += separator + result.value;
diff --git a/lib/html_tag.js b/lib/html_tag.js
index 85510fa7..8c7541f2 100644
--- a/lib/html_tag.js
+++ b/lib/html_tag.js
@@ -3,16 +3,13 @@
 function htmlTag(tag, attrs, text) {
   if (!tag) throw new TypeError('tag is required!');
 
-  var result = '<' + tag;
+  let result = `<${tag}`;
 
-  for (var i in attrs) {
-    if (
-      attrs[i] !== undefined
-      && attrs[i] !== null
-    ) result += ' ' + i + '="' + attrs[i] + '"';
+  for (const i in attrs) {
+    if (attrs[i] != null) result += ` ${i}="${attrs[i]}"`;
   }
 
-  result += text == null ? '>' : '>' + text + '</' + tag + '>';
+  result += text == null ? '>' : `>${text}</${tag}>`;
 
   return result;
 }
diff --git a/lib/index.js b/lib/index.js
index eb8fd2ea..1ec2f755 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var hash = require('./hash');
+const hash = require('./hash');
 
 exports.escapeDiacritic = require('./escape_diacritic');
 exports.escapeHTML = require('./escape_html');
diff --git a/lib/pattern.js b/lib/pattern.js
index f9d07756..c2eecf8c 100644
--- a/lib/pattern.js
+++ b/lib/pattern.js
@@ -1,8 +1,8 @@
 'use strict';
 
-var escapeRegExp = require('./escape_regexp');
+const escapeRegExp = require('./escape_regexp');
 
-var rParam = /([:*])([\w?]*)?/g;
+const rParam = /([:*])([\w?]*)?/g;
 
 function Pattern(rule) {
   if (rule instanceof Pattern) {
@@ -23,18 +23,16 @@ Pattern.prototype.test = function(str) {
 };
 
 function regexFilter(rule) {
-  return function(str) {
-    return str.match(rule);
-  };
+  return str => str.match(rule);
 }
 
 function stringFilter(rule) {
-  var params = [];
+  const params = [];
 
-  var regex = escapeRegExp(rule)
+  const regex = escapeRegExp(rule)
     .replace(/\\([*?])/g, '$1')
-    .replace(rParam, function(match, operator, name) {
-      var str = '';
+    .replace(rParam, (match, operator, name) => {
+      let str = '';
 
       if (operator === '*') {
         str = '(.*)?';
@@ -54,15 +52,14 @@ function stringFilter(rule) {
       return str;
     });
 
-  return function(str) {
-    var match = str.match(regex);
+  return str => {
+    const match = str.match(regex);
     if (!match) return;
 
-    var result = {};
-    var name;
+    const result = {};
 
-    for (var i = 0, len = match.length; i < len; i++) {
-      name = params[i - 1];
+    for (let i = 0, len = match.length; i < len; i++) {
+      const name = params[i - 1];
       result[i] = match[i];
       if (name) result[name] = match[i];
     }
diff --git a/lib/permalink.js b/lib/permalink.js
index 96684579..d574866e 100644
--- a/lib/permalink.js
+++ b/lib/permalink.js
@@ -1,22 +1,22 @@
 'use strict';
 
-var escapeRegExp = require('./escape_regexp');
+const escapeRegExp = require('./escape_regexp');
 
-var rParam = /:(\w+)/g;
+const rParam = /:(\w+)/g;
 
 function Permalink(rule, options) {
   if (!rule) throw new TypeError('rule is required!');
   options = options || {};
 
-  var segments = options.segments || {};
-  var params = [];
+  const segments = options.segments || {};
+  const params = [];
 
-  var regex = escapeRegExp(rule)
-    .replace(rParam, function(match, name) {
+  const regex = escapeRegExp(rule)
+    .replace(rParam, (match, name) => {
       params.push(name);
 
       if (segments.hasOwnProperty(name)) {
-        var segment = segments[name];
+        const segment = segments[name];
 
         if (segment instanceof RegExp) {
           return segment.source;
@@ -29,7 +29,7 @@ function Permalink(rule, options) {
     });
 
   this.rule = rule;
-  this.regex = new RegExp('^' + regex + '$');
+  this.regex = new RegExp(`^${regex}$`);
   this.params = params;
 }
 
@@ -38,13 +38,13 @@ Permalink.prototype.test = function(str) {
 };
 
 Permalink.prototype.parse = function(str) {
-  var match = str.match(this.regex);
-  var params = this.params;
-  var result = {};
+  const match = str.match(this.regex);
+  const { params } = this;
+  const result = {};
 
   if (!match) return;
 
-  for (var i = 1, len = match.length; i < len; i++) {
+  for (let i = 1, len = match.length; i < len; i++) {
     result[params[i - 1]] = match[i];
   }
 
@@ -52,9 +52,7 @@ Permalink.prototype.parse = function(str) {
 };
 
 Permalink.prototype.stringify = function(data) {
-  return this.rule.replace(rParam, function(match, name) {
-    return data[name];
-  });
+  return this.rule.replace(rParam, (match, name) => data[name]);
 };
 
 module.exports = Permalink;
diff --git a/lib/slugize.js b/lib/slugize.js
index 73755c46..0a749a7c 100644
--- a/lib/slugize.js
+++ b/lib/slugize.js
@@ -1,27 +1,26 @@
 'use strict';
 
-var escapeDiacritic = require('./escape_diacritic');
-var escapeRegExp = require('./escape_regexp');
+const escapeDiacritic = require('./escape_diacritic');
+const escapeRegExp = require('./escape_regexp');
 // eslint-disable-next-line no-control-regex
-var rControl = /[\u0000-\u001f]/g;
-var rSpecial = /[\s~`!@#$%^&*()\-_+=[\]{}|\\;:"'<>,.?/]+/g;
+const rControl = /[\u0000-\u001f]/g;
+const rSpecial = /[\s~`!@#$%^&*()\-_+=[\]{}|\\;:"'<>,.?/]+/g;
 
-function slugize(str, options) {
+function slugize(str, options = {}) {
   if (typeof str !== 'string') throw new TypeError('str must be a string!');
-  options = options || {};
 
-  var separator = options.separator || '-';
-  var escapedSep = escapeRegExp(separator);
+  const separator = options.separator || '-';
+  const escapedSep = escapeRegExp(separator);
 
-  var result = escapeDiacritic(str)
+  const result = escapeDiacritic(str)
     // Remove control characters
     .replace(rControl, '')
     // Replace special characters
     .replace(rSpecial, separator)
     // Remove continous separators
-    .replace(new RegExp(escapedSep + '{2,}', 'g'), separator)
+    .replace(new RegExp(`${escapedSep}{2,}`, 'g'), separator)
     // Remove prefixing and trailing separtors
-    .replace(new RegExp('^' + escapedSep + '+|' + escapedSep + '+$', 'g'), '');
+    .replace(new RegExp(`^${escapedSep}+|${escapedSep}+$`, 'g'), '');
 
   switch (options.transform) {
     case 1:
diff --git a/lib/spawn.js b/lib/spawn.js
index d8ebd0ad..13d2c4af 100644
--- a/lib/spawn.js
+++ b/lib/spawn.js
@@ -1,40 +1,39 @@
 'use strict';
 
-var spawn = require('cross-spawn');
-var Promise = require('bluebird');
-var CacheStream = require('./cache_stream');
+const spawn = require('cross-spawn');
+const Promise = require('bluebird');
+const CacheStream = require('./cache_stream');
 
-function promiseSpawn(command, args, options) {
+function promiseSpawn(command, args = [], options) {
   if (!command) throw new TypeError('command is required!');
 
-  if (!options && args && !Array.isArray(args)) {
+  if (!options && !Array.isArray(args)) {
     options = args;
     args = [];
   }
 
-  args = args || [];
   options = options || {};
 
-  return new Promise(function(resolve, reject) {
-    var task = spawn(command, args, options);
-    var verbose = options.verbose;
-    var encoding = options.hasOwnProperty('encoding') ? options.encoding : 'utf8';
-    var stdoutCache = new CacheStream();
-    var stderrCache = new CacheStream();
+  return new Promise((resolve, reject) => {
+    const task = spawn(command, args, options);
+    const verbose = options.verbose;
+    const { encoding = 'utf8' } = options;
+    const stdoutCache = new CacheStream();
+    const stderrCache = new CacheStream();
 
     if (task.stdout) {
-      var stdout = task.stdout.pipe(stdoutCache);
+      const stdout = task.stdout.pipe(stdoutCache);
       if (verbose) stdout.pipe(process.stdout);
     }
 
     if (task.stderr) {
-      var stderr = task.stderr.pipe(stderrCache);
+      const stderr = task.stderr.pipe(stderrCache);
       if (verbose) stderr.pipe(process.stderr);
     }
 
-    task.on('close', function(code) {
+    task.on('close', code => {
       if (code) {
-        var e = new Error(getCache(stderrCache, encoding));
+        const e = new Error(getCache(stderrCache, encoding));
         e.code = code;
 
         return reject(e);
@@ -47,9 +46,9 @@ function promiseSpawn(command, args, options) {
 
     // Listen to exit events if neither stdout and stderr exist (inherit stdio)
     if (!task.stdout && !task.stderr) {
-      task.on('exit', function(code) {
+      task.on('exit', code => {
         if (code) {
-          var e = new Error('Spawn failed');
+          const e = new Error('Spawn failed');
           e.code = code;
 
           return reject(e);
@@ -62,7 +61,7 @@ function promiseSpawn(command, args, options) {
 }
 
 function getCache(stream, encoding) {
-  var buf = stream.getCache();
+  const buf = stream.getCache();
   stream.destroy();
   if (!encoding) return buf;
 
diff --git a/lib/truncate.js b/lib/truncate.js
index 50775712..0dbd1dac 100644
--- a/lib/truncate.js
+++ b/lib/truncate.js
@@ -1,24 +1,22 @@
 'use strict';
 
-function truncate(str, options) {
+function truncate(str, options = {}) {
   if (typeof str !== 'string') throw new TypeError('str must be a string!');
-  options = options || {};
 
-  var length = options.length || 30;
-  var omission = options.omission || '...';
-  var separator = options.separator;
-  var omissionLength = omission.length;
+  const length = options.length || 30;
+  const omission = options.omission || '...';
+  const { separator } = options;
+  const omissionLength = omission.length;
 
   if (str.length < length) return str;
 
   if (separator) {
-    var words = str.split(separator);
-    var word = '';
-    var result = '';
-    var resultLength = 0;
+    const words = str.split(separator);
+    let result = '';
+    let resultLength = 0;
 
-    for (var i = 0, len = words.length; i < len; i++) {
-      word = words[i];
+    for (let i = 0, len = words.length; i < len; i++) {
+      const word = words[i];
 
       if (resultLength + word.length + omissionLength < length) {
         result += word + separator;
diff --git a/lib/word_wrap.js b/lib/word_wrap.js
index 9a552727..23fb6df6 100644
--- a/lib/word_wrap.js
+++ b/lib/word_wrap.js
@@ -1,17 +1,15 @@
 'use strict';
 
 // https://github.com/rails/rails/blob/v4.2.0/actionview/lib/action_view/helpers/text_helper.rb#L240
-function wordWrap(str, options) {
+function wordWrap(str, options = {}) {
   if (typeof str !== 'string') throw new TypeError('str must be a string!');
-  options = options || {};
 
-  var width = options.width || 80;
-  var regex = new RegExp('(.{1,' + width + '})(\\s+|$)', 'g');
-  var lines = str.split('\n');
-  var line = '';
+  const width = options.width || 80;
+  const regex = new RegExp(`(.{1,${width}})(\\s+|$)`, 'g');
+  const lines = str.split('\n');
 
-  for (var i = 0, len = lines.length; i < len; i++) {
-    line = lines[i];
+  for (let i = 0, len = lines.length; i < len; i++) {
+    const line = lines[i];
 
     if (line.length > width) {
       lines[i] = line.replace(regex, '$1\n').trim();
@@ -22,4 +20,3 @@ function wordWrap(str, options) {
 }
 
 module.exports = wordWrap;
-