Unions, literals and narrowing
Comes up in: Recruiter screen, Coding
This concept is being written. It gets the full five steps — explanation, predict, interview angle, practice with tests, and review cards. Here is exactly what it will cover, so you can study it elsewhere in the meantime.
What it covers
typeof,instanceof,in, equality and truthiness narrowing- control-flow analysis
- assignment narrowing
- narrowing pitfalls (
typeof null, truthiness of 0/"")
Words you will know
What you will practise
- narrow API results
- fix 5 narrowing bugs
Interview questions this answers
- How do you make the compiler warn when a new case is not handled?
- What is a type guard? Write one.