HTMLCanvasElement 上未解决的方法 captureStream

2022-01-17 00:00:00 javascript html html5-canvas typescript

canvas 元素和方法 captureStream 的情况很奇怪.根据文档 HTMLCanvasElement 有一个方法 captureStream.但是我的 Angular6 应用声称没有这种方法.

I have weird situation with canvas element and method captureStream. According to documentation HTMLCanvasElement has a method captureStream. However my Angular6 app claims that there isn't such method.

所以这段代码不起作用:

So this code won't work:

let canvas: HTMLCanvasElement;
canvas = document.createElement('canvas');
let stream = canvas.captureStream(20);

第三行失败.

这段代码运行没有任何错误:

This code runs without any error:

   let canvas: any;
   canvas = document.createElement('canvas');
   let stream = canvas.captureStream(20);

这怎么可能?我 100% 确定 HTMLCanvasElement 具有此方法，并且 document.createElement('canvas') 返回 HTMLCanvasElement.

How this is possible? I'm 100% sure that HTMLCanvasElement has this method and the document.createElement('canvas') returns HTMLCanvasElement.

推荐答案

根据MDN，看起来 captureStream 方法仍然是一个工作草案(截至 2021 年 6 月)，尽管并非所有主流浏览器都实现了它.这可能就是为什么它还不是 HTMLCanvasElement 的类型定义的一部分.

According to MDN, it looks like the captureStream method is still a working draft (as of June 2021), eventhough it is not implemented by all major browsers. That is probably why it is not yet part of the type definition for HTMLCanvasElement.

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