Typescript, Javscript null, undefined
Null is Bad
https://basarat.gitbooks.io/typescript/docs/tips/null.html
NOTE: These are Coding Guidelines for Contributors to TypeScript
https://github.com/Microsoft/TypeScript/wiki/Coding-guidelines#null-and-undefined
`null` vs. `undefined` in TypeScript land
https://medium.com/@basarat/null-vs-undefined-in-typescript-land-dc0c7a5f240a
undefined in JavaScript https://dmitripavlutin.com/7-tips-to-handle-undefined-in-javascript/