图示：
代码：
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>打开摄像头测试</title>
<link rel="stylesheet" href="./css/layui.css">
</head>
<body class="layui-container">
<div class="layui-panel">
<div style="padding: 32px;margin: auto;text-align:center;">
<h1>摄像头测试<h1>
<br>
<div id="app"><video autoplay controls id="video"></video></div>
<button id="cameraBtn" type="button" class="layui-btn">打开摄像头测试</button>
</div>
</div>
<script type="text/javascript">
document.querySelector('#cameraBtn').onclick = function() {
let constraints = {
audio: true,
video: true
};
navigator.mediaDevices.getUserMedia(constraints).then(function(stream) {
document.querySelector('#video').srcObject = stream
}).catch(function(err) {
console.log(err.name + ":" + err.message);
});
}
</script>
</body>
</html>