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A simplified implementation of redux-saga middleware
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| <!doctype html> | |
| <html lang="en"> | |
| <body> | |
| <script> | |
| const sagaMiddleware = store => gen => { | |
| var resolve, reject | |
| var done = new Promise((res, rej) => { | |
| resolve = res | |
| reject = rej | |
| }) | |
| Promise.resolve().then(nextStep) | |
| return {done} | |
| function nextStep(lastResult, isError) { | |
| try { | |
| const {value, done} = !isError ? gen.next(lastResult) : gen.throw(lastResult) | |
| if(done) { | |
| resolve(value) | |
| } | |
| else { | |
| execEffect(value).then( | |
| nextStep, | |
| error => nextStep(error, true) | |
| ) | |
| } | |
| } | |
| catch(err) { | |
| reject(err) | |
| } | |
| } | |
| function execEffect(eff) { | |
| if(eff.type === 'CALL') { | |
| return eff.fn(...eff.args) | |
| } | |
| if(eff.type === 'PUT') { | |
| return Promise.resolve(store.dispatch(eff.action)) | |
| } | |
| if(eff.type === 'SELECT') { | |
| return Promise.resolve(eff.selector ? eff.selector(store.getState) : store.getState()) | |
| } | |
| return Promise.resolve(eff) | |
| } | |
| } | |
| const state = [] | |
| const runSaga = sagaMiddleware({ | |
| getState() { | |
| return state | |
| }, | |
| dispatch(action) { | |
| state.push(action) | |
| console.log('dispatching', action) | |
| } | |
| }) | |
| const call = (fn, ...args) => ({type: 'CALL', fn, args}) | |
| const put = (action) => ({type: 'PUT', action}) | |
| const select = (selector) => ({type: 'SELECT', selector}) | |
| function delay(ms) { | |
| return new Promise(res => { | |
| setTimeout(res, ms) | |
| }) | |
| } | |
| function* saga(pauseDelay) { | |
| yield put('Action 1') | |
| console.log('pausing for', pauseDelay) | |
| yield call(delay, pauseDelay) | |
| console.log('getting state') | |
| const state = yield select() | |
| return state | |
| } | |
| runSaga(saga(1000)).done.then( | |
| result => console.log('saga terminated', result), | |
| error => console.error('saga aborted with', error) | |
| ) | |
| </script> | |
| </body> | |
| </html> |
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