我正在研究一个以名称和年龄作为参数的Person构造函数,并尝试实现一种检索所有“ Person”实例当前年龄值并输出平均值的方法。这是我的代码...

var Person = (function() {
    //private state
    var inst = 1;

    function Person(name, age) {
            this.name = name;
            this.age = age;
            Object.defineProperty(this, "age", {
                get: function() {
                    return age;
                },
                set: function(num) {
                    age = num;
                }
            });
            Object.defineProperty(this, "_id", {
                value: inst++
            });
        }

    //Attempt to return number of instances divided by all current Person weights
    Person.prototype.aveAge = function() {

        return inst;
    };
    return Person;
}());

var jim = new Person("jim", 32);
var richard = new Person("richard", 27);
richard.age = 28;
var alfie = new Person("alfie", 42);
Person.aveAge()  //Returns TypeError: Person.aveAge is not a function


我设置了一个在所有实例(实例)之间共享的变量,该变量在每次创建另一个实例并分配唯一ID时都会递增。我无法弄清楚如何使用我在底部添加的aveAge原型获得存在的所有Person实例的每个“年龄”值。当我尝试调用它甚至测试变量'inst'拥有正确数量的实例时,我也收到'TypeError:Person.aveAge不是一个函数'。有人知道我要去哪里错吗?

最佳答案

当提及一个人时,让一个人保持年龄是很奇怪的。请注意,将内容挂在__proto__上可使它们在构造函数(Person)中可用,而将内容挂在prototype上可使它们在实例中可用(richard)。如果Age已更新,则需要通过setAge完成,因此PeopleTracker知道要更新其内存。同样,在我的示例中,仅在需要时才计算平均值,而不是每个人每次想知道是什么时才计算平均值。



        var peopleTracker = {
            _count: 0,
            _ages: [],
            averageAge: 0,
            addPerson: function (age) {
                var pt = peopleTracker;

                pt._count += 1;
                pt._ages.push(age);
                pt.getAverage();
            },
            getAverage: function () {
                var sum = 0,
                    pt = peopleTracker;

                sum = pt._ages.reduce(function (a, b) {
                    return a + b;
                });

                pt.averageAge = Math.round(sum / pt._count);
            },
            update: function (oldAge, newAge) {
                var pt = peopleTracker,
                    ages = pt._ages,
                    i = ages.indexOf(oldAge);

                ages.splice(i, 1, newAge);
                pt.getAverage();
            }
        };

        var Person = function (name, age) {
            this.name = name;
            this.age = age;
            peopleTracker.addPerson(age);
        };

        Person.__proto__ = { // available from the constructor
            Constructor: Person,
            setAge: function (age) {
                var oldAge = this.age;
                this.age = age;
                peopleTracker.update(oldAge, age);
            },
            aveAge: function () {
                return peopleTracker.averageAge;
            }
        };

        Person.prototype = Person.__proto__; // now also available from the instance

        var jim = new Person("Jim", 32),
            richard = new Person("Richard", 27),
            alfie = new Person("Alfie", 42);

        Person.aveAge();  // 34
        richard.aveAge(); // 34
        richard.setAge(20);
        Person.aveAge();  // 31
        richard.aveAge(); // 31

关于javascript - 检索在对象的所有实例中保存的值,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/33324216/

10-08 22:39
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