Unable to change the value in the object - reactjs

My objective is to change the value of the object to true or false while onchanging the checkbox.
Object contains:
{
id: '12497wewrf5144',
name: 'ABC',
isVisible: 'false'
}
Here is the code:
import React, { Component } from 'react'
class Demo extends Component {
constructor(props) {
super(props)
this.state = {
demo: {}
}
}
componentDidMount() {
axios
.get('/api/random')
.then(res => {
this.setState({ demo: res.data?.[0] })
})
.catch(error => {
console.log(error)
})
}
render() {
return (
<div>
<h1>{this.state.demo.name}</h1>
<input type="checkbox" value={this.state.demo.value} />
</div>
)
}
}
export default Demo
I don't know what to write in onchange method for checkbox to only change the value within the object.
Can anyone help me in this query?

<input
type="checkbox"
value={this.state.demo.value}
onChange={(event) => {
this.setState((prevState) => ({
...prevState,
demo: { ...prevState.demo, isVisible: event.target.checked }
}));
}}
/>

Given your state ends up looking like
this.state = {
demo: {
id: "12497wewrf5144",
name: "ABC",
isVisible: "false",
value: false
}
};
You can create a change handler as such
changeHandler = e => {
e.preventDefault();
const { checked } = e.target;
this.setState(prevState => ({
...prevState, // <-- spread existing state
demo: {
...prevState.demo, // <-- spread existing demo
value: checked, // <-- save the input's checked value
}
}))
}
Attach the changeHandler to the onChange event callback
<input
type="checkbox"
onChange={this.changeHandler}
value={this.state.demo.value}
/>

Ciao, you could use onClick event like this:
...
handleClick = (e, data) => {
const demo = { ...this.state.demo };
demo.isVisible = !demo.isVisible;
this.setState({ demo });
}
...
<input type="checkbox" value={this.state.demo.value} onClick={((e) => this.handleClick(e, data))}/>
...

Related

Why my component is not changing state when I trigger the function

I am in new in React and I am trying to change the state when the user type some values in the inout. For a reason the component does not seem to work. Could anyone explain me why I am not succeeding in implementing this function? Thanks, Valentino
import React, { Component } from 'react';
class Stake extends Component {
state = ({
userStake: null
});
handleUserStake = (e) => {
e.preventDefault();
let newStake = e.target.value;
this.setState({
userStake: [...userStake, newStake]
})
}
render() {
return (
<div>
<form onSubmit={this.handleUserStake}>
<input
style={{
marginLeft: "40px",
width: "50px"
}}
type="text"
name="stake"
required
/>
</form>
</div >
);
}
}
export default Stake;
to accomplish a controlled input you should add the property value pointing to the respective state, and onChange that will handle its state update. for your onSubmit you use another handler specific to it. you should also fix your handleChange to update its value correctly:
class Stake extends Component {
state = ({
userStake: [],
input: ''
});
handleUserStake = (e) => {
let input = e.target.value;
this.setState({ input });
}
handleSubmit = () => {
e.preventDefault();
let newStake = this.state.input;
this.setState({
userStake: [...this.state.userStake, newStake],
input: '',
})
}
render() {
return (
<div>
<form onSubmit={this.handleSubmit}>
<input
style={{
marginLeft: "40px",
width: "50px"
}}
type="text"
name="stake"
value={this.state.input}
onChange={this.handleUserStake}
required
/>
</form>
</div>
);
}
}
export default Stake;
You need to first get userStake from the state
handleUserStake = (e) => {
e.preventDefault();
let newStake = e.target.value;
// you need to first get it from the state before updating
const { userStake } = this.state;
this.setState({
userStake: [...userStake, newStake]
})
}
Firstly you should create constructor for your component with state and binded `handleUserStakez method.
Because you are waiting for the submit event from form you would use ref for the input:
this.inputRef = React.createRef();
ref={this.inputRef}
Full code here:
class Stake extends Component {
constructor(props) {
super(props);
this.state = {
userStake: ""
};
this.handleUserStake = this.handleUserStake.bind(this);
this.inputRef = React.createRef();
}
handleUserStake = (e) => {
e.preventDefault();
let newStake = this.inputRef.current.value;
console.log("newStake", newStake);
this.setState({
...this.state,
userStake: newStake
});
};
render() {
return (
<div>
STATE: {this.state.userStake}
<form onSubmit={this.handleUserStake}>
<input
style={{
marginLeft: "40px",
width: "50px"
}}
type="text"
name="stake"
required
ref={this.inputRef}
/>
</form>
</div>
);
}
}
this should work ...
state = {
userStake: [],
};
handleUserStake = (e) => {
e.preventDefault();
let newStake = e.target.stake.value;
this.setState((state) => ({
userStake: [...state.userStake, newStake],
}));
};
what was problem? :-
getting value you need to add NAME from target which is form to get field value. like ...
let newStake = e.target.stake.value;
getting current state value, your were just getting userStake out of nowhere so it was giving undefined error.
this.setState((state) => ({ userStake: [...state.userStake, newStake], }));
make default value to [] for userStake in state obj.
userStake: []
I think I found the solution. The problem was that I had to write [...this.state.userStake, newStake]

how to change value of an object using reactjs

My objective is to change the value of an object and pass the modified object.
Here is the object:
{
id: '12497wewrf5144',
name: 'ABC',
isVisible: 'false'
}
Here is the code:
class Demo extends Component {
constructor(props) {
super(props)
this.state = {
demo: []
}
}
componentDidMount() {
axios
.get('/api/random')
.then(res => {
this.setState({ demo: res.data})
})
.catch(error => {
console.log(error)
})
}
render() {
return (
<div>
{this.state.demo.map((user)=>
<h1>{user.name}</h1>
<input type="checkbox" value={user.value} />
)}
</div>
)
}
}
export default Demo
I don't know what to write in onchange method for checkbox to only change the value within the object.
Note: value is string isVisible (we need to change value as boolean)
Can anyone help me in this query?
In order to change a certain key of an object you can use the following
this.setState({
...this.state,
demo: {
...this.state.demo,
isVisible: <NEW VALUE>
}
})

React: how do I use onSubmit to change state?

I'm quite new to React, and have only completed a few projects with it. I'm currently trying to create a form that, using onSubmit, changes the state of "isSubmitted" from false to true. When "isSubmitted" is true, I'd like to render another component to show the results of the selection.
What's currently happening is that onChange is working and I can see the value of "selectedI" set as state in the console.log when I change it. However, when I click submit, this state of "isSubmitted" doesn't change.
My code is below. Any help is greatly appreciated!
import React, { Component } from "react";
import Results from "../components/Results";
export class Create extends Component {
constructor(props) {
super(props);
this.state = {
selectedI: { value: "" },
// selectedC: { value: "" },
// selectedG: { value: "" },
// selectedA: { value: "" },
isSubmitted: false,
};
}
handleChange = (event) => {
this.setState({
selectedI: { value: event.target.value },
});
};
handleSubmit = (event) => {
event.preventdefault();
this.setState({
isSubmitted: true,
});
};
render() {
console.log(this.state);
return (
<>
<form onSubmit={this.handleSubmit} onChange={this.handleChange}>
<select value={this.state.value}>
{this.props.ingredient.map((ingredient) => {
return (
<option value={ingredient.strIngredient1}>
{ingredient.strIngredient1}
</option>
);
})}
</select>
<input type="submit" value="Submit" />
</form>
{this.state.isSubmitted && <Results />}
</>
);
}
}
export default Create;
Inside your handleSubmit method correct the case on preventdefault. It should be preventDefault. Note the capital D. Once corrected it should stop your page from reloading and resetting your state along with it. See the code below.
handleSubmit = (event) => {
event.preventDefault();
this.setState({
isSubmitted: true,
});
};

onChange or onKeyUp event takes previous value in ReactJS

I've created form in ReactJS. I am fetching value in common method in {key : value} paired. but I am getting previous value in method.
constructor(props) {
super(props);
{
this.state = { name: "", age: 0 };
}
}
inputChange = (key, value) => {
this.setState({ [key] : value });
console.log(this.state);
}
render() {
return (
<form>
<div>
Name : <input type="text" name="name" onKeyUp={(e) => this.inputChange('name', e.target.value)}></input>
</div>
<div>
Age : <input type="text" name="age" onKeyUp={(e) => this.inputChange('age', e.target.value)}></input>
</div>
</form>
)
}
I've attached the screenshot for better understanding.
setState enqueues a change to the state, but it doesn't happen immediately. If you need to do something after the state has changed, you can pass a second callback argument to setState:
inputChange = (key, value) => {
this.setState({ [key] : value }, () => {
console.log(this.state);
});
}
This will do exactly what you need.
class App extends Component {
constructor(props){
super(props)
this.state = {
name: '',
age: ''
}
}
handleInput(option, event){
if (option === 'name') {
this.setState({
name: event.target.value
}, () => {
console.log("Name: ", this.state.name)
});
}
else if (option === 'age'){
this.setState({
age: event.target.value
}, () => {
console.log("Age: ", this.state.age)
});
}
}
render() {
return (
<div>
<div>
<header>Name: </header>
<input type="text" onChange={this.handleInput.bind(this, 'name')}/>
<header>Age: </header>
<input type="text" onChange={this.handleInput.bind(this, 'age')}/>
</div>
</div>
);
}
}
update 2022
with functional components using useState hook this does not work longer, you have to use it in useEffect to update after rendering.
State updates from the useState() and useReducer() Hooks don't support the second callback argument. To execute a side effect after rendering, declare it in the component body with useEffect().

How to Create a Search Field in ReactJS

I'm new to react, and I'm working on a small project that uses a search bar to find data that I've gotten from my database.
The code for this component is below:
import React, { Component } from 'react';
class BodyData extends Component {
state = {
query: '',
data: [],
}
handleInputChange = () => {
this.setState({
query: this.search.value
})
this.filterArray();
}
getData = () => {
fetch(`http://localhost:4000/restaurants`)
.then(response => response.json())
.then(responseData => {
// console.log(responseData)
this.setState({
data:responseData
})
})
}
filterArray = () => {
var searchString = this.state.query;
var responseData = this.state.data
if(searchString.length > 0){
// console.log(responseData[i].name);
responseData = responseData.filter(l => {
console.log( l.name.toLowerCase().match(searchString));
})
}
}
componentWillMount() {
this.getData();
}
render() {
return (
<div className="searchForm">
<form>
<input type="text" id="filter" placeholder="Search for..." ref={input => this.search = input} onChange={this.handleInputChange}/>
</form>
<div>
{
this.state.data.map((i) =>
<p>{i.name}</p>
)
}
</div>
</div>
)
}
}
export default BodyData;
So basically, I want to update the state as I type in the query text, and have the restaurant names I've mapped be reduced till a match is found.
From what I understood, this.state.data will be filtered as I type in my query in the search bar. However when I map out this.state.data, I get the whole list of restaurants instead of what I want to see.
Ive been through a bunch of tutes, and I'm not exactly sure how to go about doing that.
Can anyone help me with this please? Any other comments on the code are also welcome. I'm here to learn :)
Thank you!
You could keep an additional piece of state called e.g. filteredData that contains all elements in data that include your query in the name, and then render that.
Example
class BodyData extends React.Component {
state = {
query: "",
data: [],
filteredData: []
};
handleInputChange = event => {
const query = event.target.value;
this.setState(prevState => {
const filteredData = prevState.data.filter(element => {
return element.name.toLowerCase().includes(query.toLowerCase());
});
return {
query,
filteredData
};
});
};
getData = () => {
fetch(`http://localhost:4000/restaurants`)
.then(response => response.json())
.then(data => {
const { query } = this.state;
const filteredData = data.filter(element => {
return element.name.toLowerCase().includes(query.toLowerCase());
});
this.setState({
data,
filteredData
});
});
};
componentWillMount() {
this.getData();
}
render() {
return (
<div className="searchForm">
<form>
<input
placeholder="Search for..."
value={this.state.query}
onChange={this.handleInputChange}
/>
</form>
<div>{this.state.filteredData.map(i => <p>{i.name}</p>)}</div>
</div>
);
}
}
Here is the code that will work for you
import React, { Component } from 'react';
class BodyData extends Component {
state = {
query: '',
data: [],
searchString:[]
}
handleInputChange = (event) => {
this.setState({
query: event.target.value
},()=>{
this.filterArray();
})
}
getData = () => {
fetch(`http://localhost:4000/restaurants`)
.then(response => response.json())
.then(responseData => {
// console.log(responseData)
this.setState({
data:responseData,
searchString:responseData
})
})
}
filterArray = () => {
let searchString = this.state.query;
let responseData = this.state.data;
if(searchString.length > 0){
// console.log(responseData[i].name);
responseData = responseData.filter(searchString);
this.setState({
responseData
})
}
}
componentWillMount() {
this.getData();
}
render() {
return (
<div className="searchForm">
<form>
<input type="text" id="filter" placeholder="Search for..." onChange={this.handleInputChange}/>
</form>
<div>
{
this.state.responseData.map((i) =>
<p>{i.name}</p>
)
}
</div>
</div>
)
}
}
export default BodyData;
There are few changes which is needed.
Set State is worked asynchronous.SO, to avoid it use arrow function when you need to do something immediately after set state.
there are 2 different keyword in es6 instead of var. Let and Const . use them instead of var.
There is no need of ref in input. you can directly get value of input by event.target.value
Enjoy Coding!!
setState method is asynchronous and it has second parameter - callback that is called when the state is applied.
You need to change handleInputChange methods.
handleInputChange = () => {
this.setState({
query: this.search.value
}, this.filterArray)
}
Few pointers I'll like to show-
setState({}) function is asynchronous, you'll have to either use functional setState and call filteredArray method as a callback. Or, call filteredArray at render, which is where your values will be updated and be reflected.
Your filterArray method is not returning / setting the filtered list of data. So what you type, even though it is getting filtered, it is not getting set / returned anywhere.

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