TypeScript 类函数不可用

我正在尝试调用 TypeScript 类的实例方法（在 ASP.NET MVC 项目中）。但是，在运行时我遇到了类似的异常0x800a01b6 - JavaScript runtime error: Object doesn't support property or method 'checkString'.

我将生成的 JavaScript 复制到jsfiddle http://jsfiddle.net/H7FL9/2/该方法似乎有效的地方。
我不是一个真正的 JavaScript 爱好者，所以非常感谢您的帮助！

到目前为止我尝试过的事情：

1. 不同的浏览器（Chrome：Uncaught TypeError: undefined is not a function, FF: TypeError: this.checkString is not a function)
2. 清除浏览器缓存
3. 删除IIS Express的临时文件
4. 清理并重建解决方案
5. 不使用 private 修饰符
6. 在另一台机器上启动项目
7. 用虚拟替换 underscore.js 调用以验证这不是问题
8. 检查实例成员是否正确设置

这是 TypeScript 代码：

class FormData {
    BlogName: string;
    CacheTimeOut: number;
    CopyrightHolder: string;
    NavBarTitle: string;
    MarkdownExtra: boolean;
    MarkdownSanitize: boolean;
    RatingActive: boolean;
    HtmlEditor: boolean;

    constructor(blogName: string, cacheTimeOut: number, copyrightHolder: string, navBarTitle: string, markdownExtra: boolean, markdownSanitize: boolean, ratingActive: boolean, htmlEditor: boolean) {
        this.BlogName = blogName;
        this.CacheTimeOut = cacheTimeOut;
        this.CopyrightHolder = copyrightHolder;
        this.NavBarTitle = navBarTitle;
        this.MarkdownExtra = markdownExtra;
        this.MarkdownSanitize = markdownSanitize;
        this.RatingActive = ratingActive;
        this.HtmlEditor = htmlEditor;
    }

    private checkString(value: string): boolean {
        return _.isString(value) && value !== '';
    }

    validate(): boolean {
        return (this.checkString(this.BlogName) && this.checkString(this.CopyrightHolder) && this.checkString(this.NavBarTitle) && _.isNumber(this.CacheTimeOut) && !_.isNull(this.MarkdownExtra) && !_.isNull(this.MarkdownSanitize) && !_.isNull(this.RatingActive));
    }       
}

//I'm calling the validate function like that (from within the same module)
var form = getFormData(); //returns a FormData instance
if (!form.validate()) {
    //foo
}

这里是生成的 JavaScript：

var FormData = (function () {
    function FormData(blogName, cacheTimeOut, copyrightHolder, navBarTitle, markdownExtra, markdownSanitize, ratingActive, htmlEditor) {
        this.BlogName = blogName;
        this.CacheTimeOut = cacheTimeOut;
        this.CopyrightHolder = copyrightHolder;
        this.NavBarTitle = navBarTitle;
        this.MarkdownExtra = markdownExtra;
        this.MarkdownSanitize = markdownSanitize;
        this.RatingActive = ratingActive;
        this.HtmlEditor = htmlEditor;
    }
    FormData.prototype.checkString = function (value) {
        return _.isString(value) && value !== '';
    };

    FormData.prototype.validate = function () {
        return (this.checkString(this.BlogName) && this.checkString(this.CopyrightHolder) && this.checkString(this.NavBarTitle) && _.isNumber(this.CacheTimeOut) && !_.isNull(this.MarkdownExtra) && !_.isNull(this.MarkdownSanitize) && !_.isNull(this.RatingActive));
    };
    return FormData;
})();

这可能是因为错误this在运行时。您可以使用 lambda 函数()=>{}代替function以确保this在生成的 JavaScript 中按词法作用域：

validate = (): boolean => {
        return (this.checkString(this.BlogName) && this.checkString(this.CopyrightHolder) && this.checkString(this.NavBarTitle) && _.isNumber(this.CacheTimeOut) && !_.isNull(this.MarkdownExtra) && !_.isNull(this.MarkdownSanitize) && !_.isNull(this.RatingActive));
    } 

请搜索什么this意味着在 javascript 和 typescript 中了解更多信息。