我有一个非常基本的Typescript应用程序，Chrome在打开我的index.html页面时抱怨如下：

出口未定义

导入未定义

app.ts

import Timer from "./models/timer";
class Startup {
    public static main() {
        // Initialize timer
        var timer = new Timer(new Date("25/12/2015 00:00:00"));
        // Start timer
        timer.start();
    }
}
Startup.main();

型号/定时器.ts

export default class Timer {
    target: Date;
    days: number;
    hours: number;
    minutes: number;
    seconds: number;
    constructor(target: Date) {
        this.target = target;
    }
    start() {
        var now = Date.now;
        alert(now);
    }
}

我使用的是Visual Studio代码，并有以下内容：

tsconfig.json

{
    "compilerOptions": {
        "target": "es5",
        "module": "commonjs",
        "sourceMap": true
    }
}

tasks.json

{
    "version": "0.1.0",
    "command": "tsc",
    "isShellCommand": true,
    "args": ["-p", "."],
    "showOutput": "silent",
    "problemMatcher": "$tsc"
}