build-url.ts

// Build URL safely in TypeScript (Deno)
//
// See:
//   https://developer.mozilla.org/ja/docs/Web/API/URL
//   https://developer.mozilla.org/ja/docs/Web/API/URLSearchParams

import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

export function buildURL(
  base: string,
  path: string,
  query: string | Iterable<string[]> | Record<string, string>,
): URL {
  const url = new URL(base);
  url.pathname = path;
  const params = new URLSearchParams(query);
  url.search = params.toString();

  return url;
}

[
  {
    // When query is string
    want: "https://www.example.com/search?foo=foofoo&bar=barbar",
    have: buildURL("https://www.example.com", "/search", "foo=foofoo&bar=barbar").href,
  },
  {
    // When query is Iterable<string[]>
    want: "https://www.example.com/search?foo=foofoo&bar=barbar",
    have: buildURL("https://www.example.com", "/search", [
      ["foo", "foofoo"],
      ["bar", "barbar"],
    ]).href,
  },
  {
    // When query is Record<string,string>
    want: "https://www.example.com/search?foo=foofoo&bar=barbar",
    have: buildURL("https://www.example.com", "/search", {
      foo: "foofoo",
      bar: "barbar"
    }).href,
  },
].map((testcase) => {
  assertEquals(testcase.want, testcase.have)
});