getInitialState
Returns the initial state of a reducer.
// JavaScript
function getInitialState(reducer)
// TypeScript
function getInitialState<S>(reducer: Reducer<S>): S
Details
getInitialState
asks the passed reducer for its initial state by calling it with an undefined
state and a dummy action, just as a Redux store would.
This helper is mainly intended for tests, where it can help improve readabilty. For example, when making assertions about a reducer's initial state, getInitialState(reducer)
is more expressive than something like reducer(undefined, { type: '' })
.
Examples
Basic usage:
import { getInitialState } from 'redux-preboiled'
const reducer = (state = 0, action) =>
action.type === 'increment' ? state + 1 : state
getInitialState(reducer)
// => 0
Usage in Jest:
import { getInitialState } from 'redux-preboiled'
const reducer = (state = 0, action) =>
action.type === 'increment' ? state + 1 : state
test('initial state is 0', () => {
expect(getInitialState(reducer)).toBe(0);
})
See Also
Testing guide
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