cumquelibero/index.js

JavaScript polyfill for the WHATWG spec of focusOptions, that enables a set of options to be passed to the focus method.

// focus - focusOptions - preventScroll polyfill
(function() {
  if (
    typeof window === "undefined" ||
    typeof document === "undefined" ||
    typeof HTMLElement === "undefined"
  ) {
    return;
  }

  var supportsPreventScrollOption = false;
  try {
    var focusElem = document.createElement("div");
    focusElem.addEventListener(
      "focus",
      function(event) {
        event.preventDefault();
        event.stopPropagation();
      },
      true
    );
    focusElem.focus(
      Object.defineProperty({}, "preventScroll", {
        get: function() {
          supportsPreventScrollOption = true;
        }
      })
    );
  } catch (e) {}

  if (
    HTMLElement.prototype.nativeFocus === undefined &&
    !supportsPreventScrollOption
  ) {
    HTMLElement.prototype.nativeFocus = HTMLElement.prototype.focus;

    var patchedFocus = function(args) {
      var actualPosition = window.scrollY || window.pageYOffset;
      this.nativeFocus();
      if (args && args.preventScroll) {
        // Hijacking the event loop order, since the focus() will trigger
        // internally an scroll that goes to the event loop
        setTimeout(function() {
          window.scroll(window.scrollX || window.pageXOffset, actualPosition);
        }, 0);
      }
    };

    HTMLElement.prototype.focus = patchedFocus;
  }
})();