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redux-legacyreducerbeginner

Basic Reducer

📖 Usage Example
function reducer(state, action) {
  if (action.type === 'INCREMENT') return state + 1
  return state
}
reducer(0, { type: 'INCREMENT' }) // → 1
reducer(5, { type: 'NOOP' })      // → 5

A reducer takes the current state and an action, and returns the next state without mutating anything.

Basic Reducer

A reducer is a pure function with the signature (state, action) => state. It receives the current state and an action object, and returns the next state without mutating anything.

function reducer(state, action) {
  if (action.type === 'INCREMENT') return state + 1
  return state
}

Challenge: Implement reducer(state, action) that returns state + 1 when the action type is 'INCREMENT', and returns the current state for any other action.

💡 Hints (2)
  • • Use an `if` statement or a `switch` to check `action.type`.
  • • Always return a value — reducers must never return `undefined`.