Bump to v4.0.0.

internal/checkGlobal.js

@@ -0,0 +1,12 @@
+/**
+ * Checks if `value` is a global object.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {null|Object} Returns `value` if it's a global object, else `null`.
+ */
+function checkGlobal(value) {
+  return (value && value.Object === Object) ? value : null;
+}
+
+export default checkGlobal;