Bump to v4.0.0.

isString.js

@@ -0,0 +1,37 @@
+define(['./isArray', './isObjectLike'], function(isArray, isObjectLike) {
+
+  /** `Object#toString` result references. */
+  var stringTag = '[object String]';
+
+  /** Used for built-in method references. */
+  var objectProto = Object.prototype;
+
+  /**
+   * Used to resolve the [`toStringTag`](http://ecma-international.org/ecma-262/6.0/#sec-object.prototype.tostring)
+   * of values.
+   */
+  var objectToString = objectProto.toString;
+
+  /**
+   * Checks if `value` is classified as a `String` primitive or object.
+   *
+   * @static
+   * @memberOf _
+   * @category Lang
+   * @param {*} value The value to check.
+   * @returns {boolean} Returns `true` if `value` is correctly classified, else `false`.
+   * @example
+   *
+   * _.isString('abc');
+   * // => true
+   *
+   * _.isString(1);
+   * // => false
+   */
+  function isString(value) {
+    return typeof value == 'string' ||
+      (!isArray(value) && isObjectLike(value) && objectToString.call(value) == stringTag);
+  }
+
+  return isString;
+});