Bump to v4.0.0.

internal/assignValue.js

@@ -0,0 +1,32 @@
+define(['../eq'], function(eq) {
+
+  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
+  var undefined;
+
+  /** Used for built-in method references. */
+  var objectProto = Object.prototype;
+
+  /** Used to check objects for own properties. */
+  var hasOwnProperty = objectProto.hasOwnProperty;
+
+  /**
+   * Assigns `value` to `key` of `object` if the existing value is not equivalent
+   * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
+   * for equality comparisons.
+   *
+   * @private
+   * @param {Object} object The object to modify.
+   * @param {string} key The key of the property to assign.
+   * @param {*} value The value to assign.
+   */
+  function assignValue(object, key, value) {
+    var objValue = object[key];
+    if ((!eq(objValue, value) ||
+          (eq(objValue, objectProto[key]) && !hasOwnProperty.call(object, key))) ||
+        (value === undefined && !(key in object))) {
+      object[key] = value;
+    }
+  }
+
+  return assignValue;
+});