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VistasHow to solve setState is always one step behind on React JS
I am a beginner. I am learning react js. I am having an problem. setState is always one step behind.
Here is a sample:
Here, when I typed i then the console is showing nothing. Next, when I typed the m it shows i and as it is one step behind.
I have created two functions named handleChange and handleKeyword. The functions are behaving the same. I searched on the internet and got useEffect() suggestion to solve the problem but that has not solved my problem or I can't properly implement it.
Here is my codes:
Home.jsx
import React, { useState, useEffect } from 'react';
import Search from '../../components/searchBar/Search';
import './home.scss';
const Home = () => {
const [search, setSearch] = useState('');
const [keyword, setKeyword] = useState('');
const handleChange = event => {
setSearch(event.target.value);
console.log('Search: ', search);
};
const handleKeyword = () => {
setKeyword(search);
console.log('Keyword:', keyword);
};
return (
<div className="container pb-5">
<Search
handleChange={handleChange}
handleKeyword={handleKeyword}
keyword={keyword}
/>
</div>
);
};
export default Home;
Search.jsx
import React from 'react';
import './search.scss'
const Search = props => {
return (
<div className="d-flex input-group justify-content-center">
<input
type="text"
className="form-control searchBox"
placeholder="Search for copyright free images & videos..."
value={props.value}
onChange={event => props.handleChange(event)}
/>
<button className="btn btn-primary" onClick={() => props.handleKeyword()}>
Search
</button>
</div>
);
};
export default Search;
How can I solve the problem?
3 Respuestas
Responde la pregunta0
In Home.jsx, you can move the console statments inside useEffect with states search and keyword as dependencies to get the updated values. This issue is because react is declarative in nature so it decides when to setState runs. It can even be batched together for performance optimisations. So useEffect can be used in such cases to listen to change in states.
import React, { useState, useEffect } from 'react';
import Search from '../../components/searchBar/Search';
import './home.scss';
const Home = () => {
const [search, setSearch] = useState('');
const [keyword, setKeyword] = useState('');
useEffect(() => {
console.log('Search: ', search);
console.log('Keyword:', keyword);
}, [search, keyword])
const handleChange = event => {
setSearch(event.target.value);
};
const handleKeyword = () => {
setKeyword(search);
};
return (
<div className="container pb-5">
<Search
handleChange={handleChange}
handleKeyword={handleKeyword}
keyword={keyword}
/>
</div>
);
};
export default Home;
0
The problem is setState just promise you that value will be updated It does not affect your code, just move console.logs outside handleClicks
So, when you set a new state and you will see a new value only after rerender component.
const handleKeyword = () => {
setKeyword(search);
console.log("Keyword:", keyword);
};
console.log("Keyword:2", keyword);
console.log("Keyword:", keyword); will be called in the first render with the old value
console.log("Keyword:2", keyword); will be called in the second render with a new value.
0
setState is async so changes to the state are not applied immediately. see here https://reactjs.org/docs/react-component.html#setstate
