Exemplo simples de CRUD utilizando Fetch_API

example_fetch.js

const url = '';
const listar = () => { 
    fetch(url).then(function(response){
        response.json().then(function(result){
            for (var key in result) {
                console.log(result[key].nome);
            }
        })
    });
};

const adicionar = () => {
    fetch(url,{
            method: "post",
            headers: {
                'Accept': 'application/json',
                'Content-Type': 'application/json'
            },
            body: JSON.stringify(
                {
                    nome:'Cadastrar'
                }
            )
        }
    )
};

const deletar = () => {
    fetch(url+'/'+ 4, {method:'delete'}).then(response => response.json());
};

const atualizar = () => {
    fetch(url + '/' + 3,{
        method:'put',
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        },
        body: JSON.stringify({
            nome:'Atualizar'
        })
    })
};