Fetch API so I dont ferget it again

fetch.js

var requestBody =
    '1=' + stuff1 + '&' +
    '2=' + stuff2 + '&' +
    '3=' + stuff3;

fetch('https://some-api.tld', {
    method: 'post',
    headers: {
        "Content-type": "application/x-www-form-urlencoded; charset=UTF-8"
    },
    body: requestBody
})
    .then((res) => {
    return res.text();
})
.then((data) => {
    if (data.includes('error')) {
        alert('shit');
    } else {
       alert(data);
    }
})