只是为了添加到@anton-s 的绝对正确答案，您还可以进行“完整”类重写：
// Create the original class
var ClassA = Class.create();
ClassA.prototype = {
initialize: function(config) {
this.config = config;
},
test: function(msg) {
console.log('Hi from class A with message ' + msg);
}
};
// Create new class extending the original class
var ClassB = Class.create(ClassA, {
// $super is a reference to the original method
test: function($super, msg) {
console.log('Hi from class B');
console.log('this.config is accessible in class B: ' + this.config);
$super(msg + ' ...')
}
});
// To make the extend an override, you can do this:
ClassA = ClassB;
// ClassA now is ClassB overriding the original ClassA
var a = new ClassA('some config data');
a.test('Call A 1');
由于所有这些仅适用于原型类，而不适用于已实例化的对象，因此我也将加入这个 hack，这几乎也是 wrap() 所做的：
// Overriding a method of an already instantiated object
// There are many ways to do this more elegantly thanks to the amazing JS scoping magic
a.origTest = a.test;
a.test = function(msg) {
console.log('Hi from the patched method');
this.origTest(msg);
}
a.test('Call A 2');
请记住，wrap() 方法更好，也可以用于类定义或具体实例。
// Wrap method of concrete instance
spConfig.getOptionLabel = spConfig.getOptionLabel.wrap(function(parentMethod, option, price) {
return parentMethod(option, price);
});
// Wrap method of class declaration
Product.Config.prototype.getOptionLabel = Product.Config.prototype.getOptionLabel.wrap(function(parentMethod, option, price) {
return parentMethod(option, price);
});