add hw2

node_modules/lodash/isString.js

@@ -0,0 +1,30 @@
+var baseGetTag = require('./_baseGetTag'),
+    isArray = require('./isArray'),
+    isObjectLike = require('./isObjectLike');
+
+/** `Object#toString` result references. */
+var stringTag = '[object String]';
+
+/**
+ * Checks if `value` is classified as a `String` primitive or object.
+ *
+ * @static
+ * @since 0.1.0
+ * @memberOf _
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is a string, else `false`.
+ * @example
+ *
+ * _.isString('abc');
+ * // => true
+ *
+ * _.isString(1);
+ * // => false
+ */
+function isString(value) {
+  return typeof value == 'string' ||
+    (!isArray(value) && isObjectLike(value) && baseGetTag(value) == stringTag);
+}
+
+module.exports = isString;