--- /dev/null
+var has = require('../internals/has');
+var ownKeys = require('../internals/own-keys');
+var getOwnPropertyDescriptorModule = require('../internals/object-get-own-property-descriptor');
+var definePropertyModule = require('../internals/object-define-property');
+
+module.exports = function (target, source) {
+ var keys = ownKeys(source);
+ var defineProperty = definePropertyModule.f;
+ var getOwnPropertyDescriptor = getOwnPropertyDescriptorModule.f;
+ for (var i = 0; i < keys.length; i++) {
+ var key = keys[i];
+ if (!has(target, key)) defineProperty(target, key, getOwnPropertyDescriptor(source, key));
+ }
+};