Bump to v4.0.0.

internal/stackSet.js

@@ -0,0 +1,36 @@
+import MapCache from './MapCache';
+import assocSet from './assocSet';
+
+/** Used as the size to enable large array optimizations. */
+var LARGE_ARRAY_SIZE = 200;
+
+/**
+ * Sets the stack `key` to `value`.
+ *
+ * @private
+ * @name set
+ * @memberOf Stack
+ * @param {string} key The key of the value to set.
+ * @param {*} value The value to set.
+ * @returns {Object} Returns the stack cache object.
+ */
+function stackSet(key, value) {
+  var data = this.__data__,
+      array = data.array;
+
+  if (array) {
+    if (array.length < (LARGE_ARRAY_SIZE - 1)) {
+      assocSet(array, key, value);
+    } else {
+      data.array = null;
+      data.map = new MapCache(array);
+    }
+  }
+  var map = data.map;
+  if (map) {
+    map.set(key, value);
+  }
+  return this;
+}
+
+export default stackSet;