Use more for-of

.internal/baseDifference.js

@@ -19,14 +19,12 @@ const LARGE_ARRAY_SIZE = 200
  * @returns {Array} Returns the new array of filtered values.
  */
 function baseDifference(array, values, iteratee, comparator) {
-  let index = -1
   let includes = arrayIncludes
   let isCommon = true
-  const { length } = array
   const result = []
   const valuesLength = values.length
 
-  if (!length) {
+  if (!array.length) {
     return result
   }
   if (iteratee) {
@@ -42,8 +40,7 @@ function baseDifference(array, values, iteratee, comparator) {
     values = new SetCache(values)
   }
   outer:
-  while (++index < length) {
-    let value = array[index]
+  for (let value of array) {
     const computed = iteratee == null ? value : iteratee(value)
 
     value = (comparator || value !== 0) ? value : 0

.internal/baseSum.js

@@ -8,11 +8,9 @@
  */
 function baseSum(array, iteratee) {
   let result
-  let index = -1
-  const { length } = array
 
-  while (++index < length) {
-    const current = iteratee(array[index])
+  for (value of array) {
+    const current = iteratee(value)
     if (current !== undefined) {
       result = result === undefined ? current : (result + current)
     }

.internal/copyObject.js

@@ -15,12 +15,7 @@ function copyObject(source, props, object, customizer) {
   const isNew = !object
   object || (object = {})
 
-  let index = -1
-  const length = props.length
-
-  while (++index < length) {
-    const key = props[index]
-
+  for (const key of props) {
     let newValue = customizer
       ? customizer(object[key], source[key], key, object, source)
       : undefined