如何在iOS 11 Safari上使用mediaDevices.enumerateDevices（）识别前后摄像头

Question

我使用getUserMedia()在iOS 11的Safari上捕获相机流。当我使用MediaDevices API获取相机列表时，标签为空白。有没有办法可靠地确定哪个摄像头指向哪个方向？

navigator.mediaDevices.enumerateDevices().then(function(devices) {
    devices.forEach(function(device) {
        if(device.kind === 'videoinput') {
            console.log(device);
            // Labels for both cameras are blank:
            // MediaDeviceInfo { deviceId: "123ABC", groupId: "", kind: "videoinput", label: "" }
        }
    });
});