打字稿：未捕获的 ReferenceError：未定义 Morph

问：

我收到以下错误：

Uncaught ReferenceError: Morph is not defined
    at sketch (sketch.ts:7)
    at new p5 (sketch.ts:28)
    at Object.<anonymous> (sketch.ts:28)
    at c (sketch.ts:28)
    at Function.r.import (sketch.ts:28)
    at sketch.ts:28

morph.ts位于同一文件夹中，这是sketch.ts：sketch.ts

import 'p5'
import './morph'


var sketch = (p: p5) => {

    const morph = new Morph();

    p.preload = () => {

    }

    p.setup = () => {
        p.createCanvas(p.windowWidth, p.windowHeight);
        morph.setup(p);
    }

    p.windowResized = () => {
        p.resizeCanvas(p.windowWidth, p.windowHeight);
    }

    p.draw = () => {
        p.background(100);
        morph.draw(p);        
    }
}

var sketchP = new p5(sketch);

为什么导入morph.ts不起作用。我错过了什么？

先谢谢你。