Preventing variable from being reset when using state

Let's say we have a variable that should not be changed with react rendering. Is this possible?, without me having to use a context or raise the variable up a hierarchy in the components.

import React, {useState,useMemo,useRef} from 'react'

const Component=()=>{

   const [state,setState] = useState(false)
   const ref = useRef(null)

   let previous = 0

   function increment(){
       previous  
       ref.current.innerHTML = `VARIABLE: ${previous}`
   }

   return (
       <div>
           <div ref={ref}>VARIABLE: {previous}</div>
           <div>
               <button onClick={increment}>Incremente Let</button>
               <button onClick={()=>{setState(!state)}}>Change State</button>
           </div>
       </div>
    )
  }

 export default Component

I know I can use state as well, but let's see that updating the variable will trigger new renders, but the variable doesn't need to be rendered, so why a state. This code is just an example

This example is a demonstration of the problem, not an actual implementation

CodePudding user response：

You could use useRef. The value will persist rerenders and changes will not trigger rerenders.

const previous = useRef(0);

function increment(){
    previous.current  ;
}

Since modifying it won't trigger a rerender, you want to make sure you're not rendering the value.

CodePudding user response：

You should use a state variable for previous instead of just a plain variable. Otherwise, if not stateful, the variable will always reset on re-render.

Also there's not need for updating the innerHTML via ref in this case since the variable is already being rendered.

//...
const [previous, setPrevious] = useState(0)

function increment(){
    setPrevious(previous   1)
}
//...