extendObservable(target, properties, decorators?, options?)

var Person = function(firstName, lastName) {

    // 在一个新实例上初始化 observable 属性

    extendObservable(this, {

        firstName: firstName,

        lastName: lastName,

        get fullName() {

            return this.firstName + " " + this.lastName

        },

        setFirstName(firstName) {

            this.firstName = firstName

        }

    }, {

        setFirstName: action

    });

}

var matthew = new Person("Matthew", "Henry");

// 向 observable 对象添加 observable 属性

extendObservable(matthew, {

    age: 353

});