对象的属性不是函数

Question

为什么会收到此错误消息Property 'shortDescr' of object #<Article> is not a function

function Article() {
        this.id = null;
        this.title = null;
        this.url = null;
        this.descr = null;
        this.media = null;
};

Article.prototype.shortDescr = function () {

        if ( this.descr.length > 100) {
            return this.descr.substring(0,80) + "..";
        } else {
            return this.descr;
        }
};

var ArticleFactory = {

    numOfArgs : 5,
    inputCheck : function(args) {
        if (args.length != this.numOfArgs) {
            throw new Error("Invalid number of arguments for class `Article`");
        };
        return true;
    },

    //Fill the properties with values from arguments
    create : function() {
        this.inputCheck(arguments);

        var counter = 0;
        var article = new Article();
        for(propertie in article) {
            article[propertie] = arguments[counter++];
        }
        return article;
    }
};

var descr = "@hughes it actually can do both. i have an object i created with: var obj = and another object that is being passed into a callback from a server, the one passed through the callback prints with the little arrow so you can open it up, the statically created one just prints [object Object] with no arrow. ";

var article = ArticleFactory.create(1,"title","url",descr,{});

console.log(article.shortDescr());

附录

console.log(JSON.stringify(article, null, 4));

{
    "id": 1,
    "title": "title",
    "url": "url",
    "descr": "@hughes it actually can do both. i have an object i created with: var obj = and another object that is being passed into a callback from a server, the one passed through the callback prints with the little arrow so you can open it up, the statically created one just prints [object Object] with no arrow. ",
    "media": {} }

证明

@dystroy是对的。

Answer 1

你在这里隐藏了这个功能：

 for(propertie in article) {
        article[propertie] = arguments[counter++];
 }

更准确地说，您遍历属性名称（包括原型链的名称）并为对象设置新值。当您使用原型的属性名称设置值时，您不会更改原型，但使用article.shortDescr找到的值将是对象之一，而不是原型之一。

你做的是一种盲目的（你甚至对财产的顺序都没有任何保证）所以我建议在这一点上改变你的设计（怎么样？我不能说因为我真的没有得到目的）。

但是如果你想保留它，你可以通过使用hasOwnProperty进行测试来跳过原型属性。