js如何检测摄像头权限 判断摄像头状态的3种检测方案！

function getCameraPermission() {
  return new Promise((resolve, reject) => {
    const constraints = { video: true, audio: false };

    navigator.mediaDevices.getUserMedia(constraints)
      .then(stream => {
        // 授权成功
        stream.getTracks().forEach(track => track.stop()); // 停止所有track，释放摄像头
        resolve(true);
      })
      .catch(error => {
        // 授权失败
        console.error("请求摄像头权限失败:", error);
        resolve(false); // 这里resolve(false)而不是reject，因为我们只是检测权限，不希望因为权限问题导致程序崩溃
      });
  });
}

getCameraPermission().then(hasPermission => {
  if (hasPermission) {
    console.log("已获得摄像头权限");
  } else {
    console.log("未获得摄像头权限");
  }
});

async function isCameraAvailable() {
  try {
    const stream = await navigator.mediaDevices.getUserMedia({ video: true, audio: false });
    const track = stream.getVideoTracks()[0];
    const isAvailable = track.readyState === 'live'; // track.readyState 可以是 "live", "ended", "muted"

    stream.getTracks().forEach(track => track.stop()); // 停止所有track，释放摄像头
    return isAvailable;
  } catch (error) {
    console.error("检测摄像头可用性失败:", error);
    return false;
  }
}

isCameraAvailable().then(available => {
  if (available) {
    console.log("摄像头可用");
  } else {
    console.log("摄像头不可用");
  }
});

function showPermissionDeniedMessage() {
  alert("摄像头权限被拒绝，请手动开启摄像头权限。\n\n" +
        "1. 打开浏览器设置。\n" +
        "2. 找到摄像头权限设置。\n" +
        "3. 允许网站访问摄像头。");
}

getCameraPermission().then(hasPermission => {
  if (hasPermission) {
    console.log("已获得摄像头权限");
  } else {
    console.log("未获得摄像头权限");
    showPermissionDeniedMessage();
  }
});