diff --git a/_baseAggregator.js b/_baseAggregator.js
index 5bf1fdddc..b5710aae5 100644
--- a/_baseAggregator.js
+++ b/_baseAggregator.js
@@ -12,7 +12,7 @@ import baseEach from './_baseEach.js';
  * @returns {Function} Returns `accumulator`.
  */
 function baseAggregator(collection, setter, iteratee, accumulator) {
-  baseEach(collection, function(value, key, collection) {
+  baseEach(collection, (value, key, collection) => {
     setter(accumulator, value, iteratee(value), collection);
   });
   return accumulator;
diff --git a/_baseClone.js b/_baseClone.js
index 41959eb47..324cce92c 100644
--- a/_baseClone.js
+++ b/_baseClone.js
@@ -19,12 +19,12 @@ import isObject from './isObject.js';
 import keys from './keys.js';
 
 /** Used to compose bitmasks for cloning. */
-var CLONE_DEEP_FLAG = 1,
-    CLONE_FLAT_FLAG = 2,
-    CLONE_SYMBOLS_FLAG = 4;
+const CLONE_DEEP_FLAG = 1;
+const CLONE_FLAT_FLAG = 2;
+const CLONE_SYMBOLS_FLAG = 4;
 
 /** `Object#toString` result references. */
-var argsTag = '[object Arguments]',
+const argsTag = '[object Arguments]',
     arrayTag = '[object Array]',
     boolTag = '[object Boolean]',
     dateTag = '[object Date]',
diff --git a/_baseConforms.js b/_baseConforms.js
index d7633c130..bd59720bc 100644
--- a/_baseConforms.js
+++ b/_baseConforms.js
@@ -9,10 +9,8 @@ import keys from './keys.js';
  * @returns {Function} Returns the new spec function.
  */
 function baseConforms(source) {
-  var props = keys(source);
-  return function(object) {
-    return baseConformsTo(object, source, props);
-  };
+  const props = keys(source);
+  return object => baseConformsTo(object, source, props);
 }
 
 export default baseConforms;
diff --git a/_baseCreate.js b/_baseCreate.js
index ad1da382b..bb546324f 100644
--- a/_baseCreate.js
+++ b/_baseCreate.js
@@ -1,7 +1,7 @@
 import isObject from './isObject.js';
 
 /** Built-in value references. */
-var objectCreate = Object.create;
+const objectCreate = Object.create;
 
 /**
  * The base implementation of `_.create` without support for assigning
@@ -11,9 +11,9 @@ var objectCreate = Object.create;
  * @param {Object} proto The object to inherit from.
  * @returns {Object} Returns the new object.
  */
-var baseCreate = (function() {
+const baseCreate = (() => {
   function object() {}
-  return function(proto) {
+  return proto => {
     if (!isObject(proto)) {
       return {};
     }
@@ -25,6 +25,6 @@ var baseCreate = (function() {
     object.prototype = undefined;
     return result;
   };
-}());
+})();
 
 export default baseCreate;
diff --git a/_baseDelay.js b/_baseDelay.js
index 8cc5e27a2..8ed06977c 100644
--- a/_baseDelay.js
+++ b/_baseDelay.js
@@ -1,5 +1,5 @@
 /** Error message constants. */
-var FUNC_ERROR_TEXT = 'Expected a function';
+const FUNC_ERROR_TEXT = 'Expected a function';
 
 /**
  * The base implementation of `_.delay` and `_.defer` which accepts `args`
@@ -15,7 +15,7 @@ function baseDelay(func, wait, args) {
   if (typeof func != 'function') {
     throw new TypeError(FUNC_ERROR_TEXT);
   }
-  return setTimeout(function() { func.apply(undefined, args); }, wait);
+  return setTimeout(() => func.apply(undefined, args), wait);
 }
 
 export default baseDelay;
diff --git a/_baseEvery.js b/_baseEvery.js
index 2154b4700..96964b9d5 100644
--- a/_baseEvery.js
+++ b/_baseEvery.js
@@ -10,8 +10,8 @@ import baseEach from './_baseEach.js';
  *  else `false`
  */
 function baseEvery(collection, predicate) {
-  var result = true;
-  baseEach(collection, function(value, index, collection) {
+  let result = true;
+  baseEach(collection, (value, index, collection) => {
     result = !!predicate(value, index, collection);
     return result;
   });
diff --git a/_baseFilter.js b/_baseFilter.js
index 4840ed609..4376c7908 100644
--- a/_baseFilter.js
+++ b/_baseFilter.js
@@ -9,8 +9,8 @@ import baseEach from './_baseEach.js';
  * @returns {Array} Returns the new filtered array.
  */
 function baseFilter(collection, predicate) {
-  var result = [];
-  baseEach(collection, function(value, index, collection) {
+  const result = [];
+  baseEach(collection, (value, index, collection) => {
     if (predicate(value, index, collection)) {
       result.push(value);
     }
diff --git a/_baseFindKey.js b/_baseFindKey.js
index 6d1932eed..d840ed875 100644
--- a/_baseFindKey.js
+++ b/_baseFindKey.js
@@ -10,8 +10,8 @@
  * @returns {*} Returns the found element or its key, else `undefined`.
  */
 function baseFindKey(collection, predicate, eachFunc) {
-  var result;
-  eachFunc(collection, function(value, key, collection) {
+  let result;
+  eachFunc(collection, (value, key, collection) => {
     if (predicate(value, key, collection)) {
       result = key;
       return false;
diff --git a/_baseFunctions.js b/_baseFunctions.js
index 35a875e96..c109f0ba4 100644
--- a/_baseFunctions.js
+++ b/_baseFunctions.js
@@ -11,9 +11,7 @@ import isFunction from './isFunction.js';
  * @returns {Array} Returns the function names.
  */
 function baseFunctions(object, props) {
-  return arrayFilter(props, function(key) {
-    return isFunction(object[key]);
-  });
+  return arrayFilter(props, key => isFunction(object[key]));
 }
 
 export default baseFunctions;
diff --git a/_baseIsNative.js b/_baseIsNative.js
index 04c185431..63b2fe17e 100644
--- a/_baseIsNative.js
+++ b/_baseIsNative.js
@@ -7,23 +7,23 @@ import toSource from './_toSource.js';
  * Used to match `RegExp`
  * [syntax characters](http://ecma-international.org/ecma-262/7.0/#sec-patterns).
  */
-var reRegExpChar = /[\\^$.*+?()[\]{}|]/g;
+const reRegExpChar = /[\\^$.*+?()[\]{}|]/g;
 
 /** Used to detect host constructors (Safari). */
-var reIsHostCtor = /^\[object .+?Constructor\]$/;
+const reIsHostCtor = /^\[object .+?Constructor\]$/;
 
 /** Used for built-in method references. */
-var funcProto = Function.prototype,
-    objectProto = Object.prototype;
+const funcProto = Function.prototype;
+const objectProto = Object.prototype;
 
 /** Used to resolve the decompiled source of functions. */
-var funcToString = funcProto.toString;
+const funcToString = funcProto.toString;
 
 /** Used to check objects for own properties. */
-var hasOwnProperty = objectProto.hasOwnProperty;
+const hasOwnProperty = objectProto.hasOwnProperty;
 
 /** Used to detect if a method is native. */
-var reIsNative = RegExp('^' +
+const reIsNative = RegExp('^' +
   funcToString.call(hasOwnProperty).replace(reRegExpChar, '\\$&')
   .replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
 );
@@ -40,7 +40,7 @@ function baseIsNative(value) {
   if (!isObject(value) || isMasked(value)) {
     return false;
   }
-  var pattern = isFunction(value) ? reIsNative : reIsHostCtor;
+  const pattern = isFunction(value) ? reIsNative : reIsHostCtor;
   return pattern.test(toSource(value));
 }
 
diff --git a/_baseMap.js b/_baseMap.js
index c607c0191..0cc1933b1 100644
--- a/_baseMap.js
+++ b/_baseMap.js
@@ -10,10 +10,10 @@ import isArrayLike from './isArrayLike.js';
  * @returns {Array} Returns the new mapped array.
  */
 function baseMap(collection, iteratee) {
-  var index = -1,
-      result = isArrayLike(collection) ? Array(collection.length) : [];
+  let index = -1;
+  const result = isArrayLike(collection) ? Array(collection.length) : [];
 
-  baseEach(collection, function(value, key, collection) {
+  baseEach(collection, (value, key, collection) => {
     result[++index] = iteratee(value, key, collection);
   });
   return result;
diff --git a/_baseMerge.js b/_baseMerge.js
index 37680f72f..dc1f309ab 100644
--- a/_baseMerge.js
+++ b/_baseMerge.js
@@ -20,13 +20,13 @@ function baseMerge(object, source, srcIndex, customizer, stack) {
   if (object === source) {
     return;
   }
-  baseFor(source, function(srcValue, key) {
+  baseFor(source, (srcValue, key) => {
     if (isObject(srcValue)) {
       stack || (stack = new Stack);
       baseMergeDeep(object, source, key, srcIndex, baseMerge, customizer, stack);
     }
     else {
-      var newValue = customizer
+      const newValue = customizer
         ? customizer(object[key], srcValue, (key + ''), object, source, stack)
         : undefined;
 
diff --git a/union.js b/union.js
index eb5979e92..145cacc9c 100644
--- a/union.js
+++ b/union.js
@@ -1,5 +1,4 @@
 import baseFlatten from './_baseFlatten.js';
-import baseRest from './_baseRest.js';
 import baseUniq from './_baseUniq.js';
 import isArrayLikeObject from './isArrayLikeObject.js';
 
@@ -19,8 +18,7 @@ import isArrayLikeObject from './isArrayLikeObject.js';
  * _.union([2], [1, 2]);
  * // => [2, 1]
  */
-var union = baseRest(function(arrays) {
-  return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true));
-});
+const union = (...arrays) =>
+  baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true));
 
 export default union;
diff --git a/unionBy.js b/unionBy.js
index 53651b1eb..a81c48961 100644
--- a/unionBy.js
+++ b/unionBy.js
@@ -1,6 +1,5 @@
 import baseFlatten from './_baseFlatten.js';
 import baseIteratee from './_baseIteratee.js';
-import baseRest from './_baseRest.js';
 import baseUniq from './_baseUniq.js';
 import isArrayLikeObject from './isArrayLikeObject.js';
 import last from './last.js';
@@ -28,12 +27,12 @@ import last from './last.js';
  * _.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
  * // => [{ 'x': 1 }, { 'x': 2 }]
  */
-var unionBy = baseRest(function(arrays) {
-  var iteratee = last(arrays);
+const unionBy = (...arrays) => {
+  let iteratee = last(arrays);
   if (isArrayLikeObject(iteratee)) {
     iteratee = undefined;
   }
   return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), baseIteratee(iteratee, 2));
-});
+};
 
 export default unionBy;
diff --git a/without.js b/without.js
index 5d994231a..21ca42f8a 100644
--- a/without.js
+++ b/without.js
@@ -1,5 +1,4 @@
 import baseDifference from './_baseDifference.js';
-import baseRest from './_baseRest.js';
 import isArrayLikeObject from './isArrayLikeObject.js';
 
 /**
@@ -22,10 +21,7 @@ import isArrayLikeObject from './isArrayLikeObject.js';
  * _.without([2, 1, 2, 3], 1, 2);
  * // => [3]
  */
-var without = baseRest(function(array, values) {
-  return isArrayLikeObject(array)
-    ? baseDifference(array, values)
-    : [];
-});
+const without = (array, ...values) =>
+  isArrayLikeObject(array) ? baseDifference(array, values) : [];
 
 export default without;
diff --git a/xor.js b/xor.js
index c406c48e2..8fd4d0f7f 100644
--- a/xor.js
+++ b/xor.js
@@ -1,5 +1,4 @@
 import arrayFilter from './_arrayFilter.js';
-import baseRest from './_baseRest.js';
 import baseXor from './_baseXor.js';
 import isArrayLikeObject from './isArrayLikeObject.js';
 
@@ -21,8 +20,7 @@ import isArrayLikeObject from './isArrayLikeObject.js';
  * _.xor([2, 1], [2, 3]);
  * // => [1, 3]
  */
-var xor = baseRest(function(arrays) {
-  return baseXor(arrayFilter(arrays, isArrayLikeObject));
-});
+const xor = (...arrays) =>
+  baseXor(arrayFilter(arrays, isArrayLikeObject));
 
 export default xor;
diff --git a/xorBy.js b/xorBy.js
index f21d8ad91..5afbb53fb 100644
--- a/xorBy.js
+++ b/xorBy.js
@@ -1,6 +1,5 @@
 import arrayFilter from './_arrayFilter.js';
 import baseIteratee from './_baseIteratee.js';
-import baseRest from './_baseRest.js';
 import baseXor from './_baseXor.js';
 import isArrayLikeObject from './isArrayLikeObject.js';
 import last from './last.js';
@@ -28,12 +27,12 @@ import last from './last.js';
  * _.xorBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
  * // => [{ 'x': 2 }]
  */
-var xorBy = baseRest(function(arrays) {
-  var iteratee = last(arrays);
+const xorBy = (...arrays) => {
+  let iteratee = last(arrays);
   if (isArrayLikeObject(iteratee)) {
     iteratee = undefined;
   }
   return baseXor(arrayFilter(arrays, isArrayLikeObject), baseIteratee(iteratee, 2));
-});
+};
 
 export default xorBy;