Safari ios 和 ipad 使用相机放大

Question

使用 getUserMedia() API 使用相机。我遇到的问题是它适用于除 iOS 和 iPad 之外的所有平台。我可以拍照，但无法缩放。我看到了这个帖子，但没有回复。我正在研究caniuse及其功能，据我所知，移动和桌面上的 Safari 都支持它。有小费吗？

if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
    navigator.mediaDevices.getUserMedia(videoConstraints)
    .then(stream => {

        setTimeout((evt) => {

            const track = stream.getVideoTracks()[0];
            const capabilities = track.getCapabilities();
            const settings = track.getSettings();

            if (('zoom' in capabilities)) {

                alert('zoom exists');
                const elemZoom = this.dom.select(`${this.el} #zoom-slider`);

                // Map zoom to a slider element.
                elemZoom.min = capabilities[`zoom`][`min`];
                elemZoom.max = capabilities[`zoom`][`max`];
                elemZoom.step = capabilities[`zoom`][`step`];
                elemZoom.value = settings[`zoom`];
                elemZoom.oninput = (event) => {
                    track.applyConstraints({
                        advanced: [{
                            zoom: event.target.value
                        }]
                    });
                }
                elemZoom.hidden = false;
            }

            elemVideo.srcObject = stream;


        }, 500);
    })
    .catch(err => {

    });
}