IOS에서 스크롤문제 해결방안.

var iOS = ( navigator.userAgent.match(/(iPad|iPhone|iPod)/g) ? true : false );

$(document).on('click touchstart', '.backtotop', function() {
    if (iOS) {
        $('html, body', parent.document).animate({ scrollTop: $("body").offset().top},1500,"easeOutQuart");
    } else {
        $('html, body').animate({ scrollTop: $("body").offset().top},1500,"easeOutQuart");
    }
});