Error: TypeError: Cannot read property ‘getDisplayMedia’ of undefined

留意这个点。

ou need https.

navigator.mediaDevices is only available in SecureContext now in Chrome 74, Firefox 68, and in the spec, which means the object will be missing in insecure contexts (http).

只在https中返回对象内容，不支持 http 。

版本要求chrome 74 + 、Firefox 68+

https://stackoverflow.com/questions/56623954/i-do-not-have-have-access-to-navigator-mediadevices-when-the-site-is-deployed-h

https://stackoverflow.com/questions/4912092/using-html5-canvas-javascript-to-take-in-browser-screenshots/6678156

https://developer.mozilla.org/en-US/docs/Web/API/Screen_Capture_API/Using_Screen_Capture#Examples

https://ourcodeworld.com/articles/read/415/how-to-create-a-screenshot-of-your-website-with-javascript-using-html2canvas

https://blog.csdn.net/trenki/article/details/106039171