MEPX
Chapter 4 of 10All chapters
  1. 1Reading is the job
  2. 2Getting oriented
  3. 3Understanding a function
  4. 4Following state
  5. 5Recognising shapes
  6. 6Reading for trouble
  7. 7Using history
  8. 8Tests as documentation
  9. 9Taking notes
  10. 10Reading in review

Chapter 4 of 10

Following state

Where values come from and go.

Trace backwards

When a value is wrong, walk backwards from where it is used to where it was set. That is usually shorter than reading forwards from the start.

  • Search for assignments to the name across the codebase.
  • Watch for shared references: two names for one object is a classic surprise.

Mutation

Code that changes data in place is harder to follow than code that returns new values, because the meaning of a variable depends on when you look at it.