htmlのページをスイッチする

switchToFlow(flow: string): void {
this.analyserNodeCallback = () => {};
Array.from(document.getElementsByClassName('flow')).map(
e => ((e as HTMLDivElement).style.display = 'none')
);
(document.getElementById(flow) as HTMLDivElement).style.display = 'block';
if (flow === 'flow-devices') {
this.startAudioPreview();
}
}

こんな書き方があるんだ・・・！