Fix iOS7 & iOS8 page visibility

fixPageVisibility.js

var pageVisibilityTimer = false;

function isIOS7orNewer() {
  return (/(iphone|ipad|ipod).+(os\s7|os\s8)/i).test(navigator.userAgent);
}

function pageVisibilityFix() {
  pageVisibilityTimer = window.setInterval(function() {
    window.scrollTo(document.body.scrollLeft, document.body.scrollTop);
  }, 500);
}

function stopPageVisibilityFix() {
  if (pageVisibilityTimer) {
    window.clearInterval(pageVisibilityTimer);
    pageVisibilityTimer = false;
  }
}

function startPageVisibilityFix() {
  if (isIOS7orNewer()) pageVisibilityFix();
}