courses/react/basics-state/

[utterances-bot]

State

Working with the useState hook

https://fireship.io/courses/react/basics-state/

[Ever-It-Lazy]

I don't understand what's going on here?

  const handleClick = () => {
    setCount((prev) => {
      setPrevCount(prev);
      setCount(count + 1);
    });
  };

1. handleClick() is an event handler function
2. it calls setCount(), which creates a function with the argument prev
   1. But where does prev get passed in? Is it the implicit event from handleClick()?
3. setPrevCount() sets the prevCount to prev...except I still don't know what prev is
4. then another setCount() runs, that sets count to count + 1
5. so now the outer setCount() (that got passed a function) sets count to...I don't know what?

[Sumit70421]

@Ever-It-Lazy the prev is implicit parameter in setCount() which keeps track of previous value. Every setFunction in useState hook has it as a parameter. In this context we want to update prevCount variable to current count, as we have to update the current count to +1.