[refactoring] Cleanup constructor

app/nodejs-v10/src/test/scala/io/scalajs/nodejs/url/URLTest.scala

@@ -12,5 +12,13 @@ class URLTest extends AnyFunSpec {
       myURL.search = "abc=xyz"
       assert(myURL.href === "https://example.org/abc?abc=xyz")
     }
+
+    it("should support base URL string") {
+      val url1 = new URL("/abc?123", "https://example.org")
+      assert(url1.href === "https://example.org/abc?123")
+
+      val url2 = new URL("/abc?123", new URL("https://example.org"))
+      assert(url2.href === "https://example.org/abc?123")
+    }
   }
 }

app/nodejs-v14/src/main/scala/io/scalajs/nodejs/url/URL.scala

@@ -5,17 +5,12 @@ import scala.scalajs.js
 import scala.scalajs.js.annotation.JSImport
 import scala.scalajs.js.|
 
-/**
-  * This module has utilities for URL resolution and parsing. Call require('url') to use it.
-  * @param input The input URL to parse
-  * @param base  The base URL to resolve against if the input is not absolute.
-  * @see https://nodejs.org/api/url.html
-  */
 @js.native
 @JSImport("url", "URL")
-class URL(input: String, base: String) extends js.Object {
-  def this(input: String, base: URL) = this(input, "")
-  def this(input: String) = this(input, "")
+class URL protected () extends js.Object {
+  def this(input: String, base: String) = this()
+  def this(input: String, base: URL) = this()
+  def this(input: String) = this()
 
   /**
     * The auth property is the username and password portion of the URL, also referred to as "userinfo".