foo.js

import { gql, useMutation } from '@apollo/client'

const QUERY = gql`
    mutation AddBook($title: String!, $published: Int!, $author: String!, $genres: [String!]!) {
        addBook(title: $title, published: $published, author: $author, genres: $genres) {
            title
            published
            author
            genres
        }
    }
`
const [addBook] = useMutation(QUERY)

addBook({
    variables: {
        title: title.value,
        published: published.value,
        author: author.value,
        genres: genres.value.split(','),
    }
})