--- /dev/null
+'use strict';
+
+var value = require('./valid-value')
+ , mixin = require('./mixin')
+
+ , defineProperty = Object.defineProperty
+ , getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor
+ , getOwnPropertyNames = Object.getOwnPropertyNames
+ , getPrototypeOf = Object.getPrototypeOf
+ , hasOwnProperty = Object.prototype.hasOwnProperty;
+
+module.exports = function (target, source) {
+ var error, end, define;
+ target = Object(value(target));
+ source = Object(value(source));
+ end = getPrototypeOf(target);
+ if (source === end) return target;
+ try {
+ mixin(target, source);
+ } catch (e) { error = e; }
+ source = getPrototypeOf(source);
+ define = function (name) {
+ if (hasOwnProperty.call(target, name)) return;
+ try {
+ defineProperty(target, name, getOwnPropertyDescriptor(source, name));
+ } catch (e) { error = e; }
+ };
+ while (source && (source !== end)) {
+ getOwnPropertyNames(source).forEach(define);
+ source = getPrototypeOf(source);
+ }
+ if (error) throw error;
+ return target;
+};