Chai and Mocha unit testing

I have have a given set of js code:

  handleTabKey(evt) {
    var code = evt.keyCode || evt.which;
    if (code === 9) {
      var activeElm = document.activeElement.getAttribute('id');
      if (activeElm === 'firstItem') {
        $('#skipToMenu').removeClass('menu-invisible').attr('aria-expanded', true);
        $('#firstItem').focus();
      }
    }
  }

I need to write unit test case for this function using Mocha and Chai.

I wrote the unit test case like below manner:

  describe('handleTabKey()', () => {
    it('Set focus to first element on tab', (e) => {
      expect(e.keyCode).to.equal(9);
      expect(e.which).to.equal(9);
      if (e.keyCode === 9 || e.which === 9) {
        $('#skipToMenu').$el = {
          removeClass: (strClass) => {
            bolRemoveClass = true;
            expect(strClass).to.equal("menu-invisible");
          }
        };
        expect(view.$el.getElementById('firstItem').focus()).to.equal(true);
      }
    });
  });

But it is not working for me. Instead it by pass the conditions within if.

Kindly help. Thanks in advance.