对象的属性不是函数

为什么我收到此错误消息 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是正确的。