URL implementation should add a trailing slash to the base

[charpeni]

React Native version:

System:
    OS: macOS 10.14.5
    CPU: (12) x64 Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
    Memory: 1002.17 MB / 32.00 GB
    Shell: 5.3 - /bin/zsh
  Binaries:
    Node: 10.15.3 - ~/.nvm/versions/node/v10.15.3/bin/node
    Yarn: 1.16.0 - /usr/local/bin/yarn
    npm: 6.4.1 - ~/.nvm/versions/node/v10.15.3/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  SDKs:
    iOS SDK:
      Platforms: iOS 12.2, macOS 10.14, tvOS 12.2, watchOS 5.2
    Android SDK:
      API Levels: 23, 25, 26, 27, 28
      Build Tools: 27.0.3, 28.0.2, 28.0.3, 29.0.0
      System Images: android-28 | Google APIs Intel x86 Atom, android-28 | Google Play Intel x86 Atom, android-29 | Google Play Intel x86 Atom
      Android NDK: 17.2.4988734
  IDEs:
    Android Studio: 3.4 AI-183.6156.11.34.5522156
    Xcode: 10.2.1/10E1001 - /usr/bin/xcodebuild
  npmPackages:
    react: 16.8.6 => 16.8.6
    react-native: 0.60.3 => 0.60.3

The current custom implementation of URL Standard incorrectly handles conjunctions between URL and base.

https://github.com/facebook/react-native/blob/45a4bec60cd330b9cecf5727c5ccf4203359c86e/Libraries/Blob/URL.js#L131-L155

Steps To Reproduce

const url = new URL('about', 'https://www.mozilla.org');
console.log(url.href);

Expected Behavior

https://www.mozilla.org/about

Actual Behavior

https://www.mozilla.orgabout

[charpeni]

Another issue related to this:

Steps To Reproduce

const url = new URL('dev', 'https://google.dev');
console.log(url.href);

Expected Behavior

https://google.dev/dev

Actual Behavior

https://google.dev

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may also label this issue as a "Discussion" or add it to the "Backlog" and I will leave it open. Thank you for your contributions.

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 7 days.