fix: align pathname, host and port in IE with other environments (#2)

- A pathname should always start with a slash.
- The implicit ports 80 (http) and 443 (https) are omitted by all other
  environments besides Internet Explorer.
- Always set an empty string as fallback.

BREAKING CHANGE: Setting an empty string as fallback value deviates
from the Node.js implementation of `url.parse`.

src/index.spec.ts

@@ -2,7 +2,7 @@ import { assert } from 'chai';
 import { parseURL } from './';
 
 describe('parseURL', () => {
-  it('returns an URL object for the given URL', () => {
+  it('returns an URL object for http://www.example.com:1234/foo?bar=1#baz', () => {
     const urlString = 'http://www.example.com:1234/foo?bar=1#baz';
     const expectedResult = {
       hash: '#baz',
@@ -16,4 +16,49 @@ describe('parseURL', () => {
     };
     assert.deepEqual(parseURL(urlString), expectedResult);
   });
+
+  it('returns an URL object for https://www.example.com', () => {
+    const urlString = 'https://www.example.com';
+    const expectedResult = {
+      hash: '',
+      host: 'www.example.com',
+      hostname: 'www.example.com',
+      href: 'https://www.example.com/',
+      pathname: '/',
+      port: '',
+      protocol: 'https:',
+      search: ''
+    };
+    assert.deepEqual(parseURL(urlString), expectedResult);
+  });
+
+  it('returns an URL object for http://www.example.com', () => {
+    const urlString = 'http://www.example.com';
+    const expectedResult = {
+      hash: '',
+      host: 'www.example.com',
+      hostname: 'www.example.com',
+      href: 'http://www.example.com/',
+      pathname: '/',
+      port: '',
+      protocol: 'http:',
+      search: ''
+    };
+    assert.deepEqual(parseURL(urlString), expectedResult);
+  });
+
+  it('returns an URL object for http://www.example.com:1234?bar=1&baz=2', () => {
+    const urlString = 'http://www.example.com:1234?bar=1&baz=2';
+    const expectedResult = {
+      hash: '',
+      host: 'www.example.com:1234',
+      hostname: 'www.example.com',
+      href: 'http://www.example.com:1234/?bar=1&baz=2',
+      pathname: '/',
+      port: '1234',
+      protocol: 'http:',
+      search: '?bar=1&baz=2'
+    };
+    assert.deepEqual(parseURL(urlString), expectedResult);
+  });
 });

src/index.ts

@@ -1,14 +1,14 @@
 import { Url as NodeURL } from 'url';
 
 export interface URL {
-  hash: string | undefined;
-  host: string | undefined;
-  hostname: string | undefined;
-  href: string | undefined;
-  pathname: string | undefined;
-  port: string | undefined;
-  protocol: string | undefined;
-  search: string | undefined;
+  hash: string;
+  host: string;
+  hostname: string;
+  href: string;
+  pathname: string;
+  port: string;
+  protocol: string;
+  search: string;
 }
 
 let a: HTMLAnchorElement;
@@ -19,6 +19,21 @@ if (typeof document !== 'undefined') {
   parse = require('url').parse;
 }
 
+// Removes port 80/443 from `port` and `host` if it does not exist on `href`.
+// Internet Explorer is the only browser that adds these ports.
+function removeImplicitPort(url: URL): URL {
+  const { host, href, pathname, port, protocol } = url;
+  if (href.indexOf(`${protocol}//${host}${pathname}`) < 0) {
+    url.port = '';
+    url.host = host.slice(0, host.length - port.length - 1);
+  }
+  return url;
+}
+
+function prependSlash(path: string): string {
+  return path.indexOf('/') === 0 ? path : `/${path}`;
+}
+
 export function parseURL(urlString: string): URL {
   let parsed: HTMLAnchorElement | NodeURL;
 
@@ -29,14 +44,14 @@ export function parseURL(urlString: string): URL {
     parsed = parse(urlString) as NodeURL;
   }
 
-  return {
-    hash: parsed.hash,
-    host: parsed.host,
-    hostname: parsed.hostname,
-    href: parsed.href,
-    pathname: parsed.pathname,
-    port: parsed.port,
-    protocol: parsed.protocol,
-    search: parsed.search
-  };
+  return removeImplicitPort({
+    hash: parsed.hash || '',
+    host: parsed.host || '',
+    hostname: parsed.hostname || '',
+    href: parsed.href || '',
+    pathname: prependSlash(parsed.pathname || ''),
+    port: parsed.port || '',
+    protocol: parsed.protocol || '',
+    search: parsed.search || ''
+  });
 }