trap focus within modal dialog

trap-focus-within-modal-dialog.js

_trapFocusWithinModal (ev, focusableNodes, callback) {
    const _kc = ev.keyCode;

    if (ev.type === 'keydown' && _kc === TAB_KEY) {
      console.log('keyboard tab on:', ev.target, focusableNodes);

      // Prevent default TAB operation.
      ev.preventDefault();

      const _maxAllowableFocusableNodesLength = focusableNodes.length - 1;

      const _oldFocusingTarget = ev.target;
      const _oldFocusingTargetIdx = focusableNodes.findIndex(el => el.isEqualNode(_oldFocusingTarget));

      let _nextFocusingTargetIdx = _oldFocusingTargetIdx + 1;

      if (_nextFocusingTargetIdx > _maxAllowableFocusableNodesLength) {
        _nextFocusingTargetIdx = 0;
      }

      const _nextFocusingTarget = focusableNodes[_nextFocusingTargetIdx];

      // Save document.activeElement before focusing the next target.
      this._activeNodeWhenModalOpened = _nextFocusingTarget;

      // Focus active node on next frame.
      window.requestAnimationFrame(_ => this._activeNodeWhenModalOpened.focus());
    }else if (_kc === ENTER_KEY || _kc === SPACE_KEY) {
      console.log('why-you-no-run-callback-in-focus-trap-method', callback, ev);
      callback(ev);
    }
  }