JSFiddle - React, Tailwind, and code Playground

JavaScript

String.prototype.addQuery = function (obj) {
  return this + "?" + Object.entries(obj).flatMap(([k, v]) => Array.isArray(v) ? v.map(e => `${k}=${encodeURIComponent(e)}`) : `${k}=${encodeURIComponent(v)}`).join("&");
}


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();