实现效果：
代码如下：
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>Document</title>
</head>
<body>
<video src=""></video>
<script type="text/javascript">
var opt = {
audio: true,
video: {
375,
height: 603
}
};
navigator.mediaDevices.getUserMedia(opt)
.then(function(mediaStream) {
var video = document.querySelector('video');
video.srcObject = mediaStream;
video.onloadedmetadata = function(e) {
video.play();
};
})
.catch(function(err) {
console.log(err.name + ": " + err.message);
}); // always check for errors at the end.
</script>
</body>
</html>