Utility functions that fit the Fetch ecosystem API philosophy

fetchutils.js

/**
Create a file-like object suitable for use with the fetch() API ecosystem

    fetch('/some/path', { method: 'POST', body: tojson({foo: 'Foo!'}) });

    // Sets the content-type of the request automatically:
    const req = new Request('/some/path', {
        mode: 'cors',
        headers: { 'Accept': 'application/json' },
        body: tojson({ foo: 'Foo!' }),
    });
    // => req.headers.get('content-type') === 'application/json'
**/
export const tojson = (data) =>
    new Blob([JSON.stringify(data)], { type: 'application/json' });

/**
Return the response body appropriate to the content-type

    fetch(...).then((rep) => rep.then(getBody).then((body) => ({
        success: rep.ok ? body : null,
        error: !rep.ok
            ? (!isEmpty(body)
                ? body
                : `${rep.status}: ${rep.statusText}`)
            : null,
        type: rep.headers.get('content-type'),
    })))
**/
export const getBody = (rep) => {
    const clen = rep.headers.get('content-length');
    if (clen === 0 || clen == null) {
        return Promise.resolve(null);
    }

    const ctype = rep.headers.get('content-type').split(';').at(0).trim();
    switch (ctype) {
        case 'application/json':
            return rep.json();
        case 'text/html':
        case 'text/xml':
        case 'image/svg+xml':
            return rep.text()
                .then((x) => new window.DOMParser().parseFromString(x, ctype));
        case 'text/csv':
        case 'text/plain':
            return rep.text();
        case 'multipart/form-data':
            return rep.formData();
        case 'text/event-stream':
            return rep.blob().then((x) => x.stream());
        default:
            return rep.blob();
    }
};

The Fetch API ecosystem