React functional component - using inline functions for handlers affects performance?

Question

When using class components it was always recommended to never do inline anonymous functions as its bad for performance i.e.

<input value{this.state.title} 
          onChange={(event) => this.setState({title: event.target.value})} />

You generally had to create a function outside of the render method called handleChange. This means that each render would NOT create a new inline anonymous function.

This brings me to functional components and useState etc..

The functional component is the render, so if I did this


[title, setTitle] = useState()

<input value{this.title} 
          onChange={(event) => this.setTitle({title: event.target.value})} />

It would be the same as creating a function because the function would be created each time anyway - inside a functional component

I know its possible to use the useCallback hooks to cache the function but its also recommended to not over use them as react is fast and using useCallback can actually be bad for simple cases.

So, this returns me to my original question.

Inside functional components should we be using inline anonymous functions ? Considering that creating a function inside a functional component would be created each time anyway.

I presume both are garbage collected anyway

Anybody know the recommended way ?

Thanks in advance

score 4 · Accepted Answer · answered Nov 29 '19 at 09:49

Using inline arrow functions is the recommended way in React Docs - Hooks API Reference. (see below)

I think useCallback would cause more of a performance impact then creating a new function each time.

function Counter({initialCount}) {
  const [count, setCount] = useState(initialCount);
  return (
    <>
      Count: {count}
      <button onClick={() => setCount(initialCount)}>Reset</button>
      <button onClick={() => setCount(prevCount => prevCount - 1)}>-</button>
      <button onClick={() => setCount(prevCount => prevCount + 1)}>+</button>
    </>
  );
}

React functional component - using inline functions for handlers affects performance?

1 Answers1