如何定义不可扩展的javascript对象

Question

I'd like to, if possible, define a javascript object that has a few properties along with getters/setters for those properties, but I don't want others to be able to add new properties to objects without extending the object definition (similar to how one would define a class in Java/C#). Is this possible to do with javascript?

Answer 1

You can use the "preventExtensions" method.

var obj = { foo: 'a' };
Object.preventExtensions(obj);

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/preventExtensions

Answer 2

In the following way, you can freeze the instances of the objects, but leave open to inheriting classes to add their own properties:

function Animal(name, action) {
    this.name = name;
    this.action = action;

    if (this.constructor === Animal) {
        Object.freeze(this);
    }

}

var dog = new Animal('rover', 'bark')

dog.run = function(){console.log('I\'m running!')}  // throws type error 

function Dog(name, action, bark) {
    Animal.call(this, name, action)
    this.bark = bark  // Animal not frozen since constructor is different 
    Object.freeze(this)
}

var puppy = new Dog('sparky', 'run', 'woof')

puppy.isTrained = false; // throws type error

See here: http://www.2ality.com/2013/06/freezing-instances.html