let arrayNomes = new Set()
    let novoArray = []
    const adicionar = () => {
        mercadorias.forEach(mercadoria => {
            if (produto === mercadoria.nome) {
                let total = item + Number(mercadoria.preco)
                setItem(Number(total))
                arrayNomes.add(mercadoria.nome)
            }
        })
        novoArray = [...arrayNomes]
        setNome(novoArray)
    }

I expected it to add a product to the array but without repeating the same item and to show all the items in the array. but it is creating an array for each item added.