Created
August 10, 2017 04:59
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bare bones of redux createStore.js
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| import isPlainObject from 'lodash/isPlainObject' | |
| import $$observable from 'symbol-observable' | |
| export var ActionTypes = { | |
| INIT: '@@redux/INIT' | |
| } | |
| export default function createStore(reducer, preloadedState, enhancer) { | |
| if (typeof preloadedState === 'function' && typeof enhancer === 'undefined') { | |
| enhancer = preloadedState | |
| preloadedState = undefined | |
| } | |
| if (typeof enhancer !== 'undefined') { | |
| if (typeof enhancer !== 'function') { | |
| throw new Error('Expected the enhancer to be a function.') | |
| } | |
| return enhancer(createStore)(reducer, preloadedState) | |
| } | |
| if (typeof reducer !== 'function') { | |
| throw new Error('Expected the reducer to be a function.') | |
| } | |
| var currentReducer = reducer | |
| var currentState = preloadedState | |
| var currentListeners = [] | |
| var nextListeners = currentListeners | |
| var isDispatching = false | |
| function ensureCanMutateNextListeners() { | |
| if (nextListeners === currentListeners) { | |
| nextListeners = currentListeners.slice() | |
| } | |
| } | |
| function getState() { | |
| return currentState | |
| } | |
| function subscribe(listener) { | |
| if (typeof listener !== 'function') { | |
| throw new Error('Expected listener to be a function.') | |
| } | |
| var isSubscribed = true | |
| ensureCanMutateNextListeners() | |
| nextListeners.push(listener) | |
| return function unsubscribe() { | |
| if (!isSubscribed) { | |
| return | |
| } | |
| isSubscribed = false | |
| ensureCanMutateNextListeners() | |
| var index = nextListeners.indexOf(listener) | |
| nextListeners.splice(index, 1) | |
| } | |
| } | |
| function dispatch(action) { | |
| if (!isPlainObject(action)) { | |
| throw new Error( | |
| 'Actions must be plain objects. ' + | |
| 'Use custom middleware for async actions.' | |
| ) | |
| } | |
| if (typeof action.type === 'undefined') { | |
| throw new Error( | |
| 'Actions may not have an undefined "type" property. ' + | |
| 'Have you misspelled a constant?' | |
| ) | |
| } | |
| if (isDispatching) { | |
| throw new Error('Reducers may not dispatch actions.') | |
| } | |
| try { | |
| isDispatching = true | |
| currentState = currentReducer(currentState, action) | |
| } finally { | |
| isDispatching = false | |
| } | |
| var listeners = currentListeners = nextListeners | |
| for (var i = 0; i < listeners.length; i++) { | |
| listeners[i]() | |
| } | |
| return action | |
| } | |
| function replaceReducer(nextReducer) { | |
| if (typeof nextReducer !== 'function') { | |
| throw new Error('Expected the nextReducer to be a function.') | |
| } | |
| currentReducer = nextReducer | |
| dispatch({ type: ActionTypes.INIT }) | |
| } | |
| function observable() { | |
| var outerSubscribe = subscribe | |
| return { | |
| subscribe(observer) { | |
| if (typeof observer !== 'object') { | |
| throw new TypeError('Expected the observer to be an object.') | |
| } | |
| function observeState() { | |
| if (observer.next) { | |
| observer.next(getState()) | |
| } | |
| } | |
| observeState() | |
| var unsubscribe = outerSubscribe(observeState) | |
| return { unsubscribe } | |
| }, | |
| [$$observable]() { | |
| return this | |
| } | |
| } | |
| } | |
| dispatch({ type: ActionTypes.INIT }) | |
| return { | |
| dispatch, | |
| subscribe, | |
| getState, | |
| replaceReducer, | |
| [$$observable]: observable | |
| } | |
| } |
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