Tampermonkey helpers

tampermonkey_helpers.js

// ==UserScript==
// ...
// @grant        GM_xmlhttpRequest
// ==/UserScript==

(function () {

    ...

    function httpRequestAsync(url,
                              handler,
                              data = null,
                              handlerExtraParam = null,
                              responseContentType = 'application/json') {
        let request = new XMLHttpRequest()
        request.onreadystatechange = e => {
            if (e.target.readyState === 4 && Math.floor(e.target.status / 100) === 2) {
                handler(e.target.responseText, handlerExtraParam)
            }
        }
        request.open(data ? 'POST' : 'GET', url, true)
        request.setRequestHeader('Content-Type', responseContentType);
        request.send(data)
    }
    
    function objectToQueryString(obj) {
        return Object.keys(obj)
            .map(key => `${key}=${encodeURIComponent(obj[key])}`)
            .join('&')
    }
})()