fetchWrapper.js

async function fetchWrapper({ url, method, headers = {}, body }) {
    const opts = { method, headers }
    if (method === 'POST' && typeof body === 'string') {
        headers['Content-Type'] = 'application/x-www-form-urlencoded'
        opts.body = body
    }
    const response = await fetch(url, opts)

    let output
    try {
        output = await response.clone().json()
    } catch (e) {
        output = await response.text()
    }

    if (typeof output == 'string') {
        return output
    }

    if (output.hasOwnProperty('error')) {
        throw output
    }

    return output
}