JavaScript

  1. no-var
  2. prefer-const
  3. guard-for-in: Simply use Object.keys instead. And for...of for iterating over the values of an object.
  • Some of these are likely already included with eslint's recommended rule-set. Check. (A) No, they aren't. See here
  • How to list all used eslint rules
  • Explain the problem with var (variable can be accessed and changed outside of block, show what issues it can cause)

TypeScript

  1. strict-boolean-expressions