diff --git a/.markdown-doctest-setup.js b/.markdown-doctest-setup.js
index fc16ea65e..cdb0bbb5c 100644
--- a/.markdown-doctest-setup.js
+++ b/.markdown-doctest-setup.js
@@ -2,8 +2,8 @@
 
 delete global['__core-js_shared__'];
 
-var _ = require('./lodash.js'),
-    globals = require('lodash-doc-globals');
+const _ = require('./lodash.js');
+const globals = require('lodash-doc-globals');
 
 module.exports = {
   'babel': false,
diff --git a/lib/common/file.js b/lib/common/file.js
index 879e96c66..8c57ab882 100644
--- a/lib/common/file.js
+++ b/lib/common/file.js
@@ -1,11 +1,11 @@
 'use strict';
 
-var _ = require('lodash'),
-    fs = require('fs-extra'),
-    glob = require('glob'),
-    path = require('path');
+const _ = require('lodash');
+const fs = require('fs-extra');
+const glob = require('glob');
+const path = require('path');
 
-var minify = require('../common/minify.js');
+const minify = require('../common/minify.js');
 
 /*----------------------------------------------------------------------------*/
 
@@ -30,8 +30,8 @@ function copy(srcPath, destPath) {
  * @returns {Object} Returns the object of compiled templates.
  */
 function globTemplate(pattern) {
-  return _.transform(glob.sync(pattern), function(result, filePath) {
-    var key = path.basename(filePath, path.extname(filePath));
+  return _.transform(glob.sync(pattern), (result, filePath) => {
+    const key = path.basename(filePath, path.extname(filePath));
     result[key] = _.template(fs.readFileSync(filePath, 'utf8'));
   }, {});
 }
@@ -64,8 +64,8 @@ function write(destPath, data) {
 /*----------------------------------------------------------------------------*/
 
 module.exports = {
-  'copy': copy,
-  'globTemplate': globTemplate,
-  'min': min,
-  'write': write
+  copy,
+  globTemplate,
+  min,
+  write
 };
diff --git a/lib/common/mapping.js b/lib/common/mapping.js
index 332f5afd4..f52b86072 100644
--- a/lib/common/mapping.js
+++ b/lib/common/mapping.js
@@ -1,8 +1,8 @@
 'use strict';
 
-var _mapping = require('../../fp/_mapping'),
-    util = require('./util'),
-    Hash = util.Hash;
+const _mapping = require('../../fp/_mapping');
+const util = require('./util');
+const Hash = util.Hash;
 
 /*----------------------------------------------------------------------------*/
 
diff --git a/lib/common/minify.js b/lib/common/minify.js
index 5e536c2b5..c47c98600 100644
--- a/lib/common/minify.js
+++ b/lib/common/minify.js
@@ -1,10 +1,10 @@
 'use strict';
 
-var _ = require('lodash'),
-    fs = require('fs-extra'),
-    uglify = require('uglify-js');
+const _ = require('lodash');
+const fs = require('fs-extra');
+const uglify = require('uglify-js');
 
-var uglifyOptions = require('./uglify.options');
+const uglifyOptions = require('./uglify.options');
 
 /*----------------------------------------------------------------------------*/
 
@@ -32,7 +32,7 @@ function minify(srcPath, destPath, callback, options) {
   if (!destPath) {
     destPath = srcPath.replace(/(?=\.js$)/, '.min');
   }
-  var output = uglify.minify(srcPath, _.defaults(options || {}, uglifyOptions));
+  const output = uglify.minify(srcPath, _.defaults(options || {}, uglifyOptions));
   fs.writeFile(destPath, output.code, 'utf-8', callback);
 }
 
diff --git a/lib/common/util.js b/lib/common/util.js
index b7850ff4c..0ae2bf77d 100644
--- a/lib/common/util.js
+++ b/lib/common/util.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var _ = require('lodash');
+const _ = require('lodash');
 
 /*----------------------------------------------------------------------------*/
 
@@ -13,7 +13,7 @@ var _ = require('lodash');
  * @returns {Object} Returns the new hash object.
  */
 function Hash(properties) {
-  return _.transform(properties, function(result, value, key) {
+  return _.transform(properties, (result, value, key) => {
     result[key] = (_.isPlainObject(value) && !(value instanceof Hash))
       ? new Hash(value)
       : value;
@@ -35,6 +35,6 @@ function pitch(error) {
 }
 
 module.exports = {
-  'Hash': Hash,
-  'pitch': pitch
+  Hash,
+  pitch
 };
diff --git a/lib/fp/build-dist.js b/lib/fp/build-dist.js
index e4764c6d7..9615f06c0 100644
--- a/lib/fp/build-dist.js
+++ b/lib/fp/build-dist.js
@@ -1,19 +1,19 @@
 'use strict';
 
-var _ = require('lodash'),
-    async = require('async'),
-    path = require('path'),
-    webpack = require('webpack');
+const _ = require('lodash');
+const async = require('async');
+const path = require('path');
+const webpack = require('webpack');
 
-var file = require('../common/file'),
-    util = require('../common/util');
+const file = require('../common/file');
+const util = require('../common/util');
 
-var basePath = path.join(__dirname, '..', '..'),
-    distPath = path.join(basePath, 'dist'),
-    fpPath = path.join(basePath, 'fp'),
-    filename = 'lodash.fp.js';
+const basePath = path.join(__dirname, '..', '..');
+const distPath = path.join(basePath, 'dist');
+const fpPath = path.join(basePath, 'fp');
+const filename = 'lodash.fp.js';
 
-var fpConfig = {
+const fpConfig = {
   'entry': path.join(fpPath, '_convertBrowser.js'),
   'output': {
     'path': distPath,
@@ -27,7 +27,7 @@ var fpConfig = {
   ]
 };
 
-var mappingConfig = {
+const mappingConfig = {
   'entry': path.join(fpPath, '_mapping.js'),
   'output': {
     'path': distPath,
diff --git a/lib/fp/build-doc.js b/lib/fp/build-doc.js
index 6edd802a2..613444957 100644
--- a/lib/fp/build-doc.js
+++ b/lib/fp/build-doc.js
@@ -1,22 +1,22 @@
 'use strict';
 
-var _ = require('lodash'),
-    fs = require('fs-extra'),
-    path = require('path');
+const _ = require('lodash');
+const fs = require('fs-extra');
+const path = require('path');
 
-var file = require('../common/file'),
-    mapping = require('../common/mapping'),
-    util = require('../common/util');
+const file = require('../common/file');
+const mapping = require('../common/mapping');
+const util = require('../common/util');
 
-var templatePath = path.join(__dirname, 'template/doc'),
-    template = file.globTemplate(path.join(templatePath, '*.jst'));
+const templatePath = path.join(__dirname, 'template/doc');
+const template = file.globTemplate(path.join(templatePath, '*.jst'));
 
-var argNames = ['a', 'b', 'c', 'd'];
+const argNames = ['a', 'b', 'c', 'd'];
 
-var templateData = {
-  'mapping': mapping,
-  'toArgOrder': toArgOrder,
-  'toFuncList': toFuncList
+const templateData = {
+  mapping,
+  toArgOrder,
+  toFuncList
 };
 
 /**
@@ -28,8 +28,8 @@ var templateData = {
  * @returns {string} Returns the named argument string.
  */
 function toArgOrder(indexes) {
-  var reordered = [];
-  _.each(indexes, function(newIndex, index) {
+  const reordered = [];
+  _.each(indexes, (newIndex, index) => {
     reordered[newIndex] = argNames[index];
   });
   return '`(' + reordered.join(', ') + ')`';
@@ -43,18 +43,15 @@ function toArgOrder(indexes) {
  * @returns {string} Returns the function list string.
  */
 function toFuncList(funcNames) {
-  var chunks = _.chunk(funcNames.slice().sort(), 5),
-      lastChunk = _.last(chunks),
-      last = lastChunk ? lastChunk.pop() : undefined;
+  let chunks = _.chunk(funcNames.slice().sort(), 5);
+  let lastChunk = _.last(chunks);
+  const lastName = lastChunk ? lastChunk.pop() : undefined;
 
   chunks = _.reject(chunks, _.isEmpty);
   lastChunk = _.last(chunks);
 
-  var result = '`' + _.map(chunks, function(chunk) {
-    return chunk.join('`, `') + '`';
-  }).join(',\n`');
-
-  if (last == null) {
+  let result = '`' + _.map(chunks, chunk => chunk.join('`, `') + '`').join(',\n`');
+  if (lastName == null) {
     return result;
   }
   if (_.size(chunks) > 1 || _.size(lastChunk) > 1) {
@@ -62,7 +59,7 @@ function toFuncList(funcNames) {
   }
   result += ' &';
   result += _.size(lastChunk) < 5 ? ' ' : '\n';
-  return result + '`' + last + '`';
+  return result + '`' + lastName + '`';
 }
 
 /*----------------------------------------------------------------------------*/
diff --git a/lib/fp/build-modules.js b/lib/fp/build-modules.js
index 9578499e7..c7acc7e63 100644
--- a/lib/fp/build-modules.js
+++ b/lib/fp/build-modules.js
@@ -1,25 +1,25 @@
 'use strict';
 
-var _ = require('lodash'),
-    async = require('async'),
-    glob = require('glob'),
-    path = require('path');
+const _ = require('lodash');
+const async = require('async');
+const glob = require('glob');
+const path = require('path');
 
-var file = require('../common/file'),
-    mapping = require('../common/mapping'),
-    util = require('../common/util');
+const file = require('../common/file');
+const mapping = require('../common/mapping');
+const util = require('../common/util');
 
-var templatePath = path.join(__dirname, 'template/modules'),
-    template = file.globTemplate(path.join(templatePath, '*.jst'));
+const templatePath = path.join(__dirname, 'template/modules');
+const template = file.globTemplate(path.join(templatePath, '*.jst'));
 
-var aryMethods = _.union(
+const aryMethods = _.union(
   mapping.aryMethod[1],
   mapping.aryMethod[2],
   mapping.aryMethod[3],
   mapping.aryMethod[4]
 );
 
-var categories = [
+const categories = [
   'array',
   'collection',
   'date',
@@ -33,7 +33,7 @@ var categories = [
   'util'
 ];
 
-var ignored = [
+const ignored = [
   '_*.js',
   'core.js',
   'core.min.js',
@@ -85,7 +85,7 @@ function isThru(name) {
  * @returns {*} Returns the metadata for `func`.
  */
 function getTemplate(moduleName) {
-  var data = {
+  const data = {
     'name': _.get(mapping.aliasToReal, moduleName, moduleName),
     'mapping': mapping
   };
@@ -113,28 +113,28 @@ function getTemplate(moduleName) {
 function build(target) {
   target = path.resolve(target);
 
-  var fpPath = path.join(target, 'fp');
+  const fpPath = path.join(target, 'fp');
 
   // Glob existing lodash module paths.
-  var modulePaths = glob.sync(path.join(target, '*.js'), {
+  const modulePaths = glob.sync(path.join(target, '*.js'), {
     'nodir': true,
-    'ignore': ignored.map(function(filename) {
+    'ignore': ignored.map(filename => {
       return path.join(target, filename);
     })
   });
 
   // Add FP alias and remapped module paths.
-  _.each([mapping.aliasToReal, mapping.remap], function(data) {
-    _.forOwn(data, function(realName, alias) {
-      var modulePath = path.join(target, alias + '.js');
+  _.each([mapping.aliasToReal, mapping.remap], data => {
+    _.forOwn(data, (realName, alias) => {
+      const modulePath = path.join(target, alias + '.js');
       if (!_.includes(modulePaths, modulePath)) {
         modulePaths.push(modulePath);
       }
     });
   });
 
-  var actions = modulePaths.map(function(modulePath) {
-    var moduleName = path.basename(modulePath, '.js');
+  const actions = modulePaths.map(modulePath => {
+    const moduleName = path.basename(modulePath, '.js');
     return file.write(path.join(fpPath, moduleName + '.js'), getTemplate(moduleName));
   });
 
diff --git a/lib/fp/template/doc/wiki.jst b/lib/fp/template/doc/wiki.jst
index 85ee91e42..8473e9ab3 100644
--- a/lib/fp/template/doc/wiki.jst
+++ b/lib/fp/template/doc/wiki.jst
@@ -131,8 +131,8 @@ Methods with unchanged argument orders:<br>
 <%= toFuncList(_.keys(mapping.skipRearg)) %>
 
 Methods with custom argument orders:<br>
-<%= _.map(_.keys(mapping.methodRearg), function(methodName) {
-  var orders = mapping.methodRearg[methodName];
+<%= _.map(_.keys(mapping.methodRearg), methodName => {
+  const orders = mapping.methodRearg[methodName];
   return ' * `_.' + methodName + '` has an order of ' + toArgOrder(orders);
 }).join('\n') %>
 
@@ -148,8 +148,8 @@ Methods created to accommodate Lodash’s variadic methods:<br>
 #### Aliases
 
 There are <%= _.size(mapping.aliasToReal) %> method aliases:<br>
-<%= _.map(_.keys(mapping.aliasToReal).sort(), function(alias) {
-  var realName = mapping.aliasToReal[alias];
+<%= _.map(_.keys(mapping.aliasToReal).sort(), alias => {
+  const realName = mapping.aliasToReal[alias];
   return ' * `_.' + alias + '` is an alias of `_.' + realName + '`';
 }).join('\n') %>
 
diff --git a/lib/main/build-dist.js b/lib/main/build-dist.js
index 137b6915e..35aac8261 100644
--- a/lib/main/build-dist.js
+++ b/lib/main/build-dist.js
@@ -1,17 +1,17 @@
 'use strict';
 
-var async = require('async'),
-    path = require('path');
+const async = require('async');
+const path = require('path');
 
-var file = require('../common/file'),
-    util = require('../common/util');
+const file = require('../common/file');
+const util = require('../common/util');
 
-var basePath = path.join(__dirname, '..', '..'),
-    distPath = path.join(basePath, 'dist'),
-    filename = 'lodash.js';
+const basePath = path.join(__dirname, '..', '..');
+const distPath = path.join(basePath, 'dist');
+const filename = 'lodash.js';
 
-var baseLodash = path.join(basePath, filename),
-    distLodash = path.join(distPath, filename);
+const baseLodash = path.join(basePath, filename);
+const distLodash = path.join(distPath, filename);
 
 /*----------------------------------------------------------------------------*/
 
diff --git a/lib/main/build-doc.js b/lib/main/build-doc.js
index 94003448b..a7370af69 100644
--- a/lib/main/build-doc.js
+++ b/lib/main/build-doc.js
@@ -1,20 +1,20 @@
 'use strict';
 
-var _ = require('lodash'),
-    docdown = require('docdown'),
-    fs = require('fs-extra'),
-    path = require('path');
+const _ = require('lodash');
+const docdown = require('docdown');
+const fs = require('fs-extra');
+const path = require('path');
 
-var util = require('../common/util');
+const util = require('../common/util');
 
-var basePath = path.join(__dirname, '..', '..'),
-    docPath = path.join(basePath, 'doc'),
-    readmePath = path.join(docPath, 'README.md');
+const basePath = path.join(__dirname, '..', '..');
+const docPath = path.join(basePath, 'doc');
+const readmePath = path.join(docPath, 'README.md');
 
-var pkg = require('../../package.json'),
-    version = pkg.version;
+const pkg = require('../../package.json');
+const version = pkg.version;
 
-var config = {
+const config = {
   'base': {
     'path': path.join(basePath, 'lodash.js'),
     'title': '<a href="https://lodash.com/">lodash</a> <span>v' + version + '</span>',
@@ -74,8 +74,8 @@ function postprocess(markdown) {
  * @param {string} type The format type.
  */
 function build(type) {
-  var options = _.defaults({}, config.base, config[type]),
-      markdown = docdown(options);
+  const options = _.defaults({}, config.base, config[type]);
+  const markdown = docdown(options);
 
   fs.writeFile(readmePath, postprocess(markdown), util.pitch);
 }
diff --git a/lib/main/build-modules.js b/lib/main/build-modules.js
index e9e3f365b..155e42f1b 100644
--- a/lib/main/build-modules.js
+++ b/lib/main/build-modules.js
@@ -1,16 +1,16 @@
 'use strict';
 
-var _ = require('lodash'),
-    async = require('async'),
-    path = require('path');
+const _ = require('lodash');
+const async = require('async');
+const path = require('path');
 
-var file = require('../common/file'),
-    util = require('../common/util');
+const file = require('../common/file');
+const util = require('../common/util');
 
-var basePath = path.join(__dirname, '..', '..'),
-    distPath = path.join(basePath, 'dist');
+const basePath = path.join(__dirname, '..', '..');
+const distPath = path.join(basePath, 'dist');
 
-var filePairs = [
+const filePairs = [
   [path.join(distPath, 'lodash.core.js'), 'core.js'],
   [path.join(distPath, 'lodash.core.min.js'), 'core.min.js'],
   [path.join(distPath, 'lodash.min.js'), 'lodash.min.js']
@@ -25,9 +25,8 @@ var filePairs = [
  * @param {string} target The output directory path.
  */
 function build(target) {
-  var actions = _.map(filePairs, function(pair) {
-    return file.copy(pair[0], path.join(target, pair[1]));
-  });
+  const actions = _.map(filePairs, pair =>
+    file.copy(pair[0], path.join(target, pair[1])));
 
   async.series(actions, util.pitch);
 }
diff --git a/lib/main/build-site.js b/lib/main/build-site.js
index eada119c6..69fe8c795 100644
--- a/lib/main/build-site.js
+++ b/lib/main/build-site.js
@@ -1,41 +1,41 @@
 'use strict';
 
-var _ = require('lodash'),
-    fs = require('fs'),
-    marky = require('marky-markdown'),
-    path = require('path'),
-    util = require('../common/util');
+const _ = require('lodash');
+const fs = require('fs');
+const marky = require('marky-markdown');
+const path = require('path');
+const util = require('../common/util');
 
-var basePath = path.join(__dirname, '..', '..'),
-    docPath = path.join(basePath, 'doc'),
-    readmePath = path.join(docPath, 'README.md');
+const basePath = path.join(__dirname, '..', '..');
+const docPath = path.join(basePath, 'doc');
+const readmePath = path.join(docPath, 'README.md');
+
+const highlights = [
+  'comment',
+  'constant',
+  'delimiter',
+  'html',
+  'js',
+  'method',
+  'modifier',
+  'numeric',
+  'shell',
+  'source',
+  'string',
+  'text',
+  'type'
+];
 
 function build(type) {
-  var markdown = fs
+  const markdown = fs
     // Load markdown.
     .readFileSync(readmePath, 'utf8')
     // Uncomment docdown HTML hints.
     .replace(/(<)!--\s*|\s*--(>)/g, '$1$2');
 
-  var $ = marky(markdown, { 'sanitize': false }),
-      $header = $('h1').first().remove(),
-      version = _.trim($header.find('span').first().text()).slice(1);
-
-  var highlights = [
-    'comment',
-    'constant',
-    'delimiter',
-    'html',
-    'js',
-    'method',
-    'modifier',
-    'numeric',
-    'shell',
-    'source',
-    'string',
-    'text',
-    'type'
-  ];
+  const $ = marky(markdown, { 'sanitize': false });
+  const $header = $('h1').first().remove();
+  const version = _.trim($header.find('span').first().text()).slice(1);
 
   // Remove docdown horizontal rules.
   $('hr').remove();
@@ -46,7 +46,7 @@ function build(type) {
     .attr('id', null);
 
   $(':header:not(h3) > a').each(function() {
-    var $a = $(this);
+    const $a = $(this);
     $a.replaceWith($a.html());
   });
 
@@ -54,8 +54,8 @@ function build(type) {
   $('p:empty + h3').prev().remove();
 
   $('h3 ~ p:empty').each(function() {
-    var $p = $(this),
-        node = this.previousSibling;
+    const $p = $(this);
+    let node = this.previousSibling;
 
     while ((node = node.previousSibling) && node.name != 'h3' && node.name != 'p') {
       $p.prepend(node.nextSibling);
@@ -63,19 +63,19 @@ function build(type) {
   });
 
   $('h3 code em').parent().each(function() {
-    var $code = $(this);
+    const $code = $(this);
     $code.html($code.html().replace(/<\/?em>/g, '_'));
   });
 
   // Cleanup highlights class names.
   $('.highlight [class]').each(function() {
-    var $el = $(this),
-        className = _.intersection($el.attr('class').split(/\s+/), highlights).join(' ');
+    const $el = $(this);
+    const className = _.intersection($el.attr('class').split(/\s+/), highlights).join(' ');
 
     $el.attr('class', className || null);
   });
 
-  var html = [
+  const html = [
     // Append YAML front matter.
     '---',
     'id: docs',