Union types allow a value to be one of several types (e.g., string | number). Use them when a value can legitimately have multiple types.
Advanced answer
Deep dive
Expanding on the short answer — what usually matters in practice:
Context (tags): types, union
Explain the "why", not just the "what" (intuition + consequences).
Trade-offs: what you gain/lose (time, memory, complexity, risk).
Edge cases: empty inputs, large inputs, invalid inputs, concurrency.
Examples
A tiny example (an explanation template):
// Example: discuss trade-offs for "what-are-union-types-and-when-do-you-use-them?"
function explain() {
// Start from the core idea:
// Union types allow a value to be one of several types (e.g., string | number). Use them whe
}
Common pitfalls
Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).