JS Built-ins
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redux-legacyreducerbeginner

Multiple Action Types

📖 Usage Example
function reducer(state = 0, action) {
  switch (action.type) {
    case 'INCREMENT': return state + 1
    case 'DECREMENT': return state - 1
    default: return state
  }
}
reducer(5, { type: 'DECREMENT' }) // → 4

A switch statement handles multiple action types cleanly; the default case ensures the reducer always returns a valid state.

Multiple Action Types

When a reducer handles several action types, a switch statement keeps the code clean and readable:

switch (action.type) {
  case 'INCREMENT': return state + 1
  case 'DECREMENT': return state - 1
  default: return state
}

The default case is essential — it handles unknown actions (including Redux's internal @@INIT).

Challenge: Implement reducer(state = 0, action) that handles 'INCREMENT', 'DECREMENT', and any other action via the default case.

💡 Hints (2)
  • • A switch statement is idiomatic Redux — each `case` handles one action type.
  • • Always include a `default: return state` to handle any action you haven't handled explicitly.