Move internal modules to “internal” folder.

.internal/arrayLikeKeys.js

@@ -0,0 +1,44 @@
+import baseTimes from './.internal/baseTimes.js';
+import isArguments from './isArguments.js';
+import isBuffer from './isBuffer.js';
+import isIndex from './.internal/isIndex.js';
+import isTypedArray from './isTypedArray.js';
+
+/** Used to check objects for own properties. */
+const hasOwnProperty = Object.prototype.hasOwnProperty;
+
+/**
+ * Creates an array of the enumerable property names of the array-like `value`.
+ *
+ * @private
+ * @param {*} value The value to query.
+ * @param {boolean} inherited Specify returning inherited property names.
+ * @returns {Array} Returns the array of property names.
+ */
+function arrayLikeKeys(value, inherited) {
+  const isArr = Array.isArray(value);
+  const isArg = !isArr && isArguments(value);
+  const isBuff = !isArr && !isArg && isBuffer(value);
+  const isType = !isArr && !isArg && !isBuff && isTypedArray(value);
+  const skipIndexes = isArr || isArg || isBuff || isType;
+  const result = skipIndexes ? baseTimes(value.length, String) : [];
+  const length = result.length;
+
+  for (const key in value) {
+    if ((inherited || hasOwnProperty.call(value, key)) &&
+        !(skipIndexes && (
+           // Safari 9 has enumerable `arguments.length` in strict mode.
+           (key == 'length' ||
+           // Node.js 0.10 has enumerable non-index properties on buffers.
+           (isBuff && (key == 'offset' || key == 'parent')) ||
+           // PhantomJS 2 has enumerable non-index properties on typed arrays.
+           (isType && (key == 'buffer' || key == 'byteLength' || key == 'byteOffset')) || // Skip index properties.
+           isIndex(key, length))
+        ))) {
+      result.push(key);
+    }
+  }
+  return result;
+}
+
+export default arrayLikeKeys;