javascript 类，只读属性，闭包

function employee(_name, _dept){
this.getName = (function(){ return _name; })();
this.getDept = (function(){ return _dept; })();
}

employee.prototype={ say:'hello' }//父类赋值

var x = new employee('test1',2);//x继承

console.log(x.say);

x.__proto__={say:'hi'};//x改自己的

console.log(x.say);

var y = new employee('test2', 1);//y继承

console.log(y.say);

y.__proto__.say = 'are you ok?';//y改父类的

console.log(y.say);

var z = new employee('test3');//z继承

console.log(z.say);