This is a keyboard I wrote for a 3-hour interview question in 2009 after roughly 1 year of JavaScript development experience. The keyboard had to be rendered purely with JavaScript, write to a <textarea>, and have any other features that seemed useful. I tacked on a "shift" key in the final minutes of the time limit, and it worked.

No 3rd party libraries were allowed, and it had to work in Safari and Firefox. There were some brownie points for working in Internet Explorer, but it wasn't a requirement. Chrome had just been released but wasn't a requirement yet.

https://ssorallen.github.io/vanillajs-keyboard/