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subscribe to throw when listener is not a function #1325

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Merged
merged 5 commits into from
Jan 30, 2016
Merged

subscribe to throw when listener is not a function #1325

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d575747
Added check to createStore.subscribe to ensure listener is a function
JamieDixon Jan 30, 2016
40fd771
Replaced error message with correct arg name
JamieDixon Jan 30, 2016
0c51819
Removed semi-colon from end of toThrow()
JamieDixon Jan 30, 2016
5279a93
Added tests for more deta types passed to createStore.subscribe
JamieDixon Jan 30, 2016
69f8d97
Removed extra new line after last assertion
JamieDixon Jan 30, 2016
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4 changes: 4 additions & 0 deletions src/createStore.js
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,10 @@ export default function createStore(reducer, initialState, enhancer) {
* @returns {Function} A function to remove this change listener.
*/
function subscribe(listener) {
if (typeof listener !== 'function') {
throw new Error('Expected listener to be a function.')
}

listeners.push(listener)
var isSubscribed = true

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20 changes: 20 additions & 0 deletions test/createStore.spec.js
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Expand Up @@ -548,4 +548,24 @@ describe('createStore', () => {
store.replaceReducer(() => {})
).toNotThrow()
})

it('throws if listener is not a function', () => {
const store = createStore(reducers.todos)

expect(() =>
store.subscribe()
).toThrow()
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Let's check a few more data types: null, undefined, and string should throw.

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Added a few extra checks for the types mentioned. I've gone with the assertion style I've seen elsewhere rather than something like:

const cases = [undefined, null, ''];
    cases.map(arg =>
      expect(() =>
        store.subscribe(arg))
      .toThrow())


expect(() =>
store.subscribe('')
).toThrow()

expect(() =>
store.subscribe(null)
).toThrow()

expect(() =>
store.subscribe(undefined)
).toThrow()
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Nit: please remove the extra newline

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+1 removed in latest commit.

})
})