visibility change

index.js

export function onVisibilityChange(cb) {
  let hidden;
  let visibilityChange;
  if (typeof document.hidden !== "undefined") {
    // Opera 12.10 and Firefox 18 and later support
    hidden = "hidden";
    visibilityChange = "visibilitychange";
  } else if (typeof document.msHidden !== "undefined") {
    hidden = "msHidden";
    visibilityChange = "msvisibilitychange";
  } else if (typeof document.webkitHidden !== "undefined") {
    hidden = "webkitHidden";
    visibilityChange = "webkitvisibilitychange";
  }

  document.addEventListener(visibilityChange, handleVisibilityChange);

  function handleVisibilityChange() {
    cb(!document[hidden]);
  }
}

onVisibilityChange((visible) => {
  if (visible) {
    // page is visible
  } else {
    // page is hidden
  }
});