class Timer {

//js 内置的timer对象

    private _jsInnerTimerObj: any;

    private _enable: boolean;

    private _handlerInvoker:any;

    private _interval: number;

    get Interval(): number{

        return this._interval;

    }

    set Interval(value: number) {

        this._interval = value;

        //重新设定新的定时器

        if (this._jsInnerTimerObj) {

            window.clearInterval(this._jsInnerTimerObj);

        }

    }

    private _elapsed:any;

    get Elapsed(): any{

        return this._elapsed;

    }

    set Elapsed(value: any) {

        /*if (!isFunction(value)) {

            throw new Error("the Elapsed value must be function!");

        }*/

        this._elapsed = value;

        //只有设置了触发事件才定时，没有回调的定时器是无意义的定时执行其中的匿名方法

        this._jsInnerTimerObj = window.setInterval(this._handlerInvoker, this.Interval);     

    }

    /*  构造函数

    *@interval 设置定时器的毫秒数

    */

    constructor(interval: number) {

        this._enable = false;

        this.Interval = interval;

        var that = this;

        this._handlerInvoker = function () {

             if (that.Elapsed&&that._enable==true){

                that.Elapsed();

             }

        }

    }

    Start() {

        this._enable = true;

    }

    Stop() {

        this._enable = false;

    }

}

var t = new Timer(500);

t.Elapsed = function () {

   document.write(99)

}

t.Start();