How to detect is device is MacOS

let isMac = navigator.platform.toUpperCase().indexOf('MAC')>=0;

if(!isMac){
	let bgAttachment = document.querySelectorAll('.bg-attachment');
			for (i = 0; i < bgAttachment.length; i++){
					bgAttachment[i].classList.add('ios-device');					
			}
}

if(isMac){
		let bgAttachmentLanding = document.querySelectorAll('.section-header-img');
	for (i = 0; i < bgAttachmentLanding.length; i++){
					bgAttachmentLanding[i].classList.add('allow-animation');					
			}
}