chore: cleanup

[deuchainn]

Rather than adding more comments to the PR here, i created PR on your PR what has been done is the following:

1. Run prettier + eslint linter on the code
2. Replacement of var with let and const
3. Prefer const rather than let, whenever the value is immutable
4. Use string literals e.g. One: ${one} two: ${two} rather than string concatenation.
5. Spaces between functions, if it makes sense to group them could use block grouping with region folding like e.g. // #region group many editors supports this, or just group by adding some comments.