add hw2

node_modules/ramda/es/internal/_isArray.js

@@ -0,0 +1,15 @@
+/**
+ * Tests whether or not an object is an array.
+ *
+ * @private
+ * @param {*} val The object to test.
+ * @return {Boolean} `true` if `val` is an array, `false` otherwise.
+ * @example
+ *
+ *      _isArray([]); //=> true
+ *      _isArray(null); //=> false
+ *      _isArray({}); //=> false
+ */
+export default Array.isArray || function _isArray(val) {
+  return val != null && val.length >= 0 && Object.prototype.toString.call(val) === '[object Array]';
+};