The value passed to the element selector function (usually $w), must be of type string

How would I go about doing that I’m new to coding
const menuItems = {
Home : {

  button :  '#Home' , 

  underline :  '#HomeLine' , 

  //contentBox: '#HomeBox' 

},

Shop : {

  button :  '#Shop' , 

  underline :  '#ShopLine' , 

  contentBox :  '#ShopBox' 

},

FAQ : {

  button :  '#FAQ' , 

  underline :  '#FAQLine' , 

  //contentBox: '#kidsBox' 

},

About : {

  button :  '#About' , 

  underline :  '#AboutLine' , 

  //contentBox: '#kidsBox' 

  }, 

$w.onReady( function () {
initMegaMenu()
});

function initMegaMenu () {
for (let i in menuItems) {
$w(menuItems[i].button).onMouseIn(() => {
openRelevantPanel(menuItems[i]);
});

$w(menuItems[i].contentBox).onMouseOut(() => {
openRelevantPanel();
});
}
}

async function openRelevantPanel ( hoverItem ) {
for ( let i in menuItems) {
if (menuItems[i] === hoverItem) {
$w(menuItems[i].underline).show();
await $w(menuItems[i].contentBox).expand();
} else {
$w(menuItems[i].underline).hide();
$w(menuItems[i].contentBox).collapse();
}
}
}