Fix 6 Maintainability issues in multiple files

[intv0id]

CodeFactor found multiple issues:

Trailing whitespace

src\tgraph.ts:45 src\optimizer.ts:110

For (... in ...) statements must be filtered with an if statement

src\graphTypes.ts:129-149

Throwing plain strings (not instances of Error) gives no stack traces

src\utils.ts:11

Assignments in conditional expressions are forbidden

src\utils.ts:26

'node' is defined but never used.

examples\main.js:14