- Fix long line.
- Enforce a few stylistic habits:
- Avoid some potential dangerous constructs.
- `arrow-spacing`: Use at least one space around arrows.
- `keyword-spacing`: Use at least one space around keywords (if, else, for…).
- `no-multiple-empty-lines`: Only use one empty line between code.
- `no-var`: Use `let` or `const` instead of `var`:
- `padded-blocks`: Do not pad blocks.
- `padding-line-between-statements`: Use empty lines between some statements.
- `space-before-blocks`: Use at least one space before the opening brace of a block.