fix: fix default base as per URL spec (#133)

The default value for base was an empty string which is strong, base is an optional param and so should be undefined.

https://url.spec.whatwg.org/#url-class

BREAKING CHANGE: behaviour of the constructor may break some use cases, but at least now it implements the spec correctly.

.gitignore

@@ -12,3 +12,4 @@ node_modules
 .nyc_output
 coverage.lcov
 yarn-error.log
+package-lock.json

src/url-browser.js

@@ -1,8 +1,6 @@
 'use strict';
 
-const defaultBase = self.location ?
-    self.location.protocol + '//' + self.location.host :
-    '';
+const defaultBase = self.location && self.location.protocol + '//' + self.location.host;
 const URL = self.URL;
 
 class URLWithLegacySupport {

test.js

@@ -9,6 +9,26 @@ const isBrowser =
     typeof document === 'object' &&
     document.nodeType === 9;
 
+test('unspecified base should not throw', (t) => {
+    t.plan(1);
+
+    if (isBrowser) {
+        t.doesNotThrow(() => new URL('http://localhost'));
+    } else {
+        // Hack to force construction of a browser URL in Node to simulate a React Native-like environment where .location does not exist
+        global.self = {
+            URL: global.URL,
+            URLSearchParams: global.URLSearchParams
+        };
+        /* eslint-disable-next-line global-require */
+        const { URLWithLegacySupport: URL } = require('./src/url-browser');
+
+        t.doesNotThrow(() => new URL('http://localhost'));
+
+        delete global.self;
+    }
+});
+
 test('relative', (t) => {
     t.plan(1);