URLSearchParams: URLSearchParams() constructor

new URLSearchParams()
new URLSearchParams(options)

// Retrieve params via url.search, passed into constructor
const url = new URL("https://example.com?foo=1&bar=2");
const params1 = new URLSearchParams(url.search);

// Get the URLSearchParams object directly from a URL object
const params1a = url.searchParams;

// Pass in a string literal
const params2 = new URLSearchParams("foo=1&bar=2");
const params2a = new URLSearchParams("?foo=1&bar=2");

// Pass in a sequence of pairs
const params3 = new URLSearchParams([
  ["foo", "1"],
  ["bar", "2"],
]);

// Pass in a record
const params4 = new URLSearchParams({ foo: "1", bar: "2" });

const url = new URL("https://example.com/?a=hello&b=world");

console.log(url.href);
// https://example.com/?a=hello&b=world

console.log(url.origin);
// https://example.com

const addParams = {
  c: "a",
  d: 2,
  e: false,
};

const newParams = new URLSearchParams([
  ...Array.from(url.searchParams.entries()), // [["a","hello"],["b","world"]]
  ...Object.entries(addParams), // [["c","a"],["d",2],["e",false]]
]).toString();
console.log(newParams);
// a=hello&b=world&c=a&d=2&e=false

const newURL = new URL(`${url.origin}${url.pathname}?${newParams}`);

console.log(newURL.href);
// https://example.com/?a=hello&b=world&c=a&d=2&e=false

// Here it is as a function that accepts (URL, Record<string, string>)
const addSearchParams = (url, params = {}) =>
  new URL(
    `${url.origin}${url.pathname}?${new URLSearchParams([
      ...Array.from(url.searchParams.entries()),
      ...Object.entries(params),
    ])}`,
  );