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Redux: Implementing store from scratch

In redux, store is a very central piece which brings actions, reducers and states together. It has the following main functions and API :

Holds application state;
Allows access to state via getState();
Allows state to be updated via dispatch(action);
Registers listeners via subscribe(listener);
Handles unregistering of listeners via the function returned by subscribe(listener);.

Redux Store

[wpgist id="dcb86657def2bd9390a170b8a4f17092" file="store.js"]

Note: The subscribe function returns another function, which filters out the listener from the list of listeners. Hence, if you want to unsubscribe a listener then you will have to save the reference for the return value while subscribing and call the reference function. For example,


let foo = () => {...};

let unsubscribeFoo = store.subscribe(foo); // At this point foo will be called whenever the store updates

// sometime in future
unsubscribeFoo(); // After this function is executed, the foo will not be called whenever the store updates

store 1