Bump to v4.0.0.

isFunction.js

@@ -0,0 +1,41 @@
+define(['./isObject'], function(isObject) {
+
+  /** `Object#toString` result references. */
+  var funcTag = '[object Function]',
+      genTag = '[object GeneratorFunction]';
+
+  /** 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 `Function` object.
+   *
+   * @static
+   * @memberOf _
+   * @category Lang
+   * @param {*} value The value to check.
+   * @returns {boolean} Returns `true` if `value` is correctly classified, else `false`.
+   * @example
+   *
+   * _.isFunction(_);
+   * // => true
+   *
+   * _.isFunction(/abc/);
+   * // => false
+   */
+  function isFunction(value) {
+    // The use of `Object#toString` avoids issues with the `typeof` operator
+    // in Safari 8 which returns 'object' for typed array constructors, and
+    // PhantomJS 1.9 which returns 'function' for `NodeList` instances.
+    var tag = isObject(value) ? objectToString.call(value) : '';
+    return tag == funcTag || tag == genTag;
+  }
+
+  return isFunction;
+});