[DOCS ISSUE] Page: Front end helper methods #226

Hello everybody, i'm a french junior dev on apostrophecms3.
Here is my problem :
I have a customer module with a favorites field :

favorites: {
label: 'apostrophe:favorites',
type: 'array',
titleField: 'favorite',
fields: {
add: {
type: {
type: 'string',
label: 'apostrophe:favoriteType',
},
id: {
type: 'string',
label: 'apostrophe:favoriteId',
},
}
}
},

I would like to add a new favorite for this customer by clicking a button on the article page.

But i can't find the way to do it in my index.js front file.

Here is a part of my code :

favorite.addEventListener('click', () => {

      addFavorite(favorite.id)  // favorite.id is defined
   
    })

async function addFavorite(favoriteId) {

  const customerId = sessionStorage.getItem('aposCustomerId')

  try {
    
        ???? what's going on here ????
  
  } catch (err) {
    console.error(err)
  } finally {
  }
}

Thanks a lot for your help !