[BUG]: QuickType web interface fails to load

[foxt]

Issue Type

When attempting to load https://app.quicktype.io

Context (Environment, Version, Language)

Input Format: JSON Output Language: TypeScript

CLI, npm, or app.quicktype.io: app.quicktype.io

Description

When loading the QuickType interface in a browser, the site does not load (shows blank page) and the following error is logged to the console:

Uncaught (in promise) Error: Unknown language name: TypeScript
    at Object.O (main-DDOXwfaa.js:1120:4178)
    at T8e (main-DDOXwfaa.js:2864:7554)
    at _8e (main-DDOXwfaa.js:2864:8047)
    at C8e (main-DDOXwfaa.js:2864:8401)
    at main-DDOXwfaa.js:2864:8416

Expected Behaviour / Output

The app works

Current Behaviour / Output

You get a blank page.

Steps to Reproduce

Load an old version of QuickType, change language to 'TypeScript' and then attempt to load the latest version.

Possible Solution

It appears, at some point the IDs of the languages was changed from capitalised (i.e. TypeScript) to all lowercase (typescript), and if the user has saved preferences with a capitalised language name, in the new version, it will fail to find a language with that ID and due to missing error handling, the application fails to load.

Related: #2755 #2764

If you are encountering this issue and just want a quick work around:

Either clear browsing data for the domain via your browser's settings, or open your browser's developer tools (F12), go to the 'Console' tab, and enter localStorage.clear() and reload the page.