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VisualizaçõesPreventing variable from being reset when using state - React
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
2 Respostas
Responde à pergunta0
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.
0
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)
}
//...