JSFiddle - React, Tailwind, and code Playground

JavaScript

var obj = {
    param1: 'something',
    param2: 'somethingelse',
    param3: 'another',
    bla: {
        param5: 'i\'m nested!',
        ja: {
            param6: 'i am really nested'
        }
    }
};

var serialiseObject = function(obj) {
    var pairs = [];
    for (var prop in obj) {
        if (!obj.hasOwnProperty(prop)) {
            continue;
        }

        if (Object.prototype.toString.call(obj[prop]) == '[object Object]') {
            pairs.push(serialiseObject(obj[prop]));
            continue;
        }

        pairs.push(prop + '=' + obj[prop]);
    }
    return pairs.join('&');
}

document.body.innerHTML = serialiseObject(obj);