JSFiddle - React, Tailwind, and code Playground

JavaScript

String.prototype.addQuery = function (obj) {
  return this + Object.keys(obj).reduce(function (p, e, i) {
    return p + (i == 0 ? "?" : "&") +
      (Array.isArray(obj[e]) ? obj[e].reduce(function (str, f, j) {
        return str + e + "=" + encodeURIComponent(f) + (j != obj[e].length - 1 ? "&" : "")
      }, "") : e + "=" + encodeURIComponent(obj[e]));
  }, "");
}


function myFunction() {
  const url = "https://sampleUrl";
  const query = {
    query1: ["value1A", "value1B", "value1C"],
    query2: "value2A, value2B",
    query3: "value3A/value3B",
  };
  const endpoint = url.addQuery(query);
  console.log(endpoint);
}

myFunction();