How Zustand's SetState Leverages Closures In JavaScript

In this article, I will provide a review on how setState in Zustand’s source code is written/works. This concept leverages closures in JavaScript and arrow functions.

StoreApi type is straight forward.

export interface StoreApi<T> {
  setState: SetStateInternal<T>
  getState: () => T
  getInitialState: () => T
  subscribe: (listener: (state: T, prevState: T) => void) => () => void
}

    
    

    
    




setState accepts two parameters

partial 
replace

Let’s perform an experiment using the example demo app provided in theZustand repo.
I added some console statements in the dist to see...