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How to change the state in react with a form

I have a form that is supposed to update the initial state, I've followed many tutorials and my code looks the same as them but for some reason it doesn't update the state.
import React, { Component } from 'react';
class Create extends Component{
constructor(props){
super(props);
this.state = {
title: "",
body: "",
error: ""
}
}
onTitleChange(e) {
const title = e.target.value;
this.setState({title})
}
onBodyChange(e) {
const body = e.target.value;
this.setState({body})
}
onSubmit(e) {
e.preventDefault();
if(!this.state.title || !this.state.body){
this.setState(() => ({ error: "Please fill in all gaps"}))
} else {
this.setState(() => ({ error: "" }))
// Send info to the main page
alert(this.state.title);
}
}
render(){
return(
<div>
{this.state.error && <p>{this.state.error}</p>}
<form onSubmit = {this.onSubmit}>
<label>Put a title for your note</label>
<input
placeholder="Title"
type="text"
value={this.state.title}
autoFocus
onChange= {this.onTitleChange}
/>
<label>Write your note</label>
<textarea
placeholder="Note"
value={this.state.body}
autoFocus
onChange = {this.onBodyChange}
/>
<input type="submit" value="Submit"/>
</form>
</div>
);
}
}
export default Create;
When I check the current state in the React developer tools it shows that the state remains the same and I don't know why because there are not errors in the log.
I'm working with webpack, babel and react.
////////////////////
EDITED
////////////////////
I edited my code following the suggestions you guys gave me but still it doesn't work. An alert is supposed to appear when submitted the form but that doesn't get fired either, so I believe that non of the functions are getting fired.
This is my edited code:
import React, { Component } from 'react';
class Create extends Component{
constructor(props){
super(props);
this.onTitleChange = this.onTitleChange.bind(this);
this.onBodyChange = this.onBodyChange.bind(this);
this.onSubmit = this.onSubmit.bind(this);
this.state = {
title: "",
body: "",
error: ""
}
}
onTitleChange(e) {
const title = e.target.value;
this.setState((prevState) => {
return {
...prevState,
title
};
});
}
onBodyChange(e) {
const body = e.target.value;
this.setState((prevState) => {
return {
...prevState,
body
};
});
}
onSubmit(e) {
e.preventDefault();
if(!this.state.title || !this.state.body){
this.setState((prevState) => {
return {
...prevState,
error: "Please fill in all gaps"
};
});
} else {
this.setState((prevState) => {
return {
...prevState,
error: ""
};
});
// Send info to the main page
alert(this.state.title);
}
}
render(){
return(
<div>
{this.state.error && <p>{this.state.error}</p>}
<form onSubmit = {this.onSubmit}>
<label>Put a title for your note</label>
<input
placeholder="Title"
type="text"
value={this.state.title}
autoFocus
onChange= {this.onTitleChange}
/>
<label>Write your note</label>
<textarea
placeholder="Note"
value={this.state.body}
autoFocus
onChange = {this.onBodyChange}
/>
<input type="submit" value="Submit"/>
</form>
</div>
);
}
}
export default Create;

You should try binding the event handlers in the constructor, because it seems like this within those event handling functions could be undefined. The React documentation outlines why the binding is necessary, and here's another useful page on handling forms in React.
constructor(props) {
super(props);
...
this.onTitleChange = this.onTitleChange.bind(this);
this.onBodyChange = this.onBodyChange.bind(this);
this.onSubmitChange = this.onSubmitChange.bind(this);
}
An alternative to binding in the constructor would also be to use arrow functions for your event handlers which implicitly bind this.
class Create extends Component {
...
onTitleChange = () => { ... }
onBodyChange = () => { ... }
onSubmitChange = () => { ... }
}
EDIT: Can't comment on your post since my reputation is too low, but it seems like there's a typo in the changes you just made.
this.onSubmitC = this.onSubmit.bind(this) should be changed to
this.onSubmit = this.onSubmit.bind(this)

React's setState() accepts an object, not a function. So change your onSubmit() to this:
if(!this.state.title || !this.state.body){
this.setState({ error: "Please fill in all gaps"})
} else {
this.setState({ error: "" })
// Send info to the main page
alert(this.state.title);
}

It better to use the previous state and only update the required (input value) values.
in your case you are replacing the existing state (whole object) just with the title and the same goes for body onBodyChange
onTitleChange () {
const title = e.target.value;
this.setState((prevState) => {
return {
...prevState,
title
};
});
};
<

React-Redux: State always one input behind

I've created a class based component that renders an input field. I need the global state to update while the user types into the input. The issue is that the global state is always one step (render?) behind from what's actually in the input field. For example, when I write “winners” in the input, the state is “winner” instead. How can I fix this?
Component
class TeamCardT1 extends Component {
constructor(props) {
super(props);
// local state
this.state = {
team_one_name: "Team One",
};
// bind events
this.handleName = this.handleName.bind(this);
};
handleName = e => {
this.setState({
...this.state,
team_one_name: e.target.value
});
this.props.handleSubmit(this.state);
};
render() {
const { team_one_name } = this.state;
return (
<>
<div className="teamCard_container">
<input
type="text"
id="team_one_name"
name="team_one_name"
value={team_one_name}
onChange={this.handleName}
maxLength="35"
minLength="2"
className="teamCard_teamName" />
<PlayersCardT1 />
<ScoreCard />
</div>
</>
)
};
}
index.js for the component
const mapStateToProps = ({ team_one_name }) => {
return {
team_one_name,
};
};
// Dispatch
const mapDispatchToProps = dispatch => {
return {
handleSubmit: (data) => { dispatch(updateTeamOneName(data)) }
};
};
export default connect(mapStateToProps, mapDispatchToProps)(TeamCardT1);

You handleSubmit with the previous state, change to the current value.
handleName = e => {
this.setState({ team_one_name: e.target.value });
this.props.handleSubmit(e.target.value);
};
Notice that you already have a shallow merge with setState so you don't need to destruct this.state.

state is one step behind because you should call the prop function as a setState callback by this way the prop function will call just after the state set.
handleName = e => {
this.setState({
...this.state,
team_one_name: e.target.value
}, () => {
this.props.handleSubmit({value: e.target.value});
});
};

React Component State Being Reset to Default

I am trying to track a form in this.state with event handlers on the inputs, but for some reason this.state is being reset back to its default state when the event handler tries to update it. This is an example of what the Component looks like.
class ExampleReport extends React.Component {
constructor(props) {
super(props)
this.state = {
reportDetails: null,
report: this.props.report,
form: {}
}
this.textInputHandler = this.textInputHandler.bind(this)
}
textInputHandler(e) {
var reportForm = this.state.form;
var target = e.target;
var name = target.className;
var value = target.value;
reportForm[name] = value;
this.setState({ form: reportForm })
}
render(){
return(
<form>
<input className="example" type="text" onChange={(e) => {this.textInputHandler(e)}} />
</form>
)
}
}
Before textInputHandler is called, this.state has an object and array stored in it, but once setState is called they are reset back to the default in the constructor. On subsequent updates to the text input this.state.form persists but everything else is reset. How can I prevent this from happening?
UPDATE
After trying some of the solutions suggested below I went back and logged this.state at just about every possible point and found that it is reset even before setState() is being called in the input handler.

You forget about input value and update state by ref (make mutation).
class ExampleReport extends React.Component {
constructor(props) {
super(props)
this.state = {
reportDetails: null,
report: this.props.report,
form: { example: '', },
}
this.textInputHandler = this.textInputHandler.bind(this)
}
textInputHandler(e) {
const { target: { name, value } } = e;
this.setState(prevState => ({
...prevState,
form: {
...prevState.form,
[name]: value,
},
}));
}
render() {
const { form: { example } } = this.state;
return (
<form>
<input
className="example"
type="text"
name="example"
value={example}
onChange={this.textInputHandler}
/>
</form>
)
}
}

Once way to solve this would be like below, spreading reportForm in a new object
textInputHandler(e) {
var reportForm = this.state.form;
var target = e.target;
var name = target.className;
var value = target.value;
reportForm[name] = value;
this.setState({ form: { ...reportForm } }) // <----------------------
}
However you may want to use more declarative solution as provided by Kirill but without unnecessary state changes
textInputHandler(e) {
const { className: name, value } = e.target;
this.setState(prevState => { form: { ...prevState.form, [name]: value } }) // <----------------------
}

try changing your onChange to this
onChange={this.textInputHandler}
like how they have it in the react documentation
EX)
<input type="text" value={this.state.value} onChange={this.handleChange} />
then do the spreading stuff
don't add, e.preventDefault because that only works for submitting
Look at Krill answer he has everything you need on there
compare it to yours from the top, you have a lot of stuff missing

How can I check the value of this.state with an if statement and not console.log()?

I want to check the values of this.state.cityCodeval and this.state.idVal using an if statement inside the displayName() method so it can display what's inside the return() if the values inputted by the user are correct.
In my Webstorm IDE, I get a warning that says:
Binary operation argument type string is not compatible with type string
Which makes me believe I'm checking for their values the wrong way.
I know I could just do console.log(this.state.cityCodeval); or console.log(this.state.idVal);, but I need to check for what the user input is.
Here's my code
import React, { Component } from 'react';
import { connect } from 'react-redux';
import * as actionType from '../../store/actions/actions';
class SearchArticle extends Component {
constructor(props) {
super(props);
this.state = {
flag: false,
idVal: '',
cityCodeval: ''
};
this.handleChange = this.handleChange.bind(this);
this.handleArticleId = this.handleArticleId.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleSubmit(event) {
event.preventDefault();
console.log("IDValue --> " + this.state.idVal);
this.props.articleIdValueRedux(this.state.idVal);
this.setState({flag: true});
}
handleChange = event => {
this.setState({value: event.target.value});
this.props.cityCodeReducerRedux(event.target.value);
}
handleArticleId = event => {
event.preventDefault();
this.setState({idVal: event.target.value});
}
displayName = () => {
if(this.state.cityCodeval === 'nyc' && this.state.idVal === '1') {
return (
<div>
<p>author name: {this.state.authorNameValue}</p>
<p>article text: {this.state.storyTextValue}</p>
</div>
);
}
}
render() {
return(
<div>
<form onSubmit={this.handleSubmit}>
<input onChange={this.handleChange} value={this.state.cityCodeValue} type="text" placeholder="city code"/>
<input onChange={this.handleArticleId} value={this.state.idVal} placeholder="article id"/>
<button type="submit" value="Search">Submit</button>
{this.state.flag ? this.displayName() : null}
</form>
</div>
);
}
}
const mapStateToProps = state => {
return {
cityCodeValue: state.cityCodeValue.cityCodeValue,
authorNameValue: state.authorNameValue.authorNameValue,
articleIdValue: state.articleIdValue.articleIdValue,
storyTextValue: state.storyTextValue.storyTextValue
};
};
const mapDispatchToProps = dispatch => {
return {
cityCodeReducerRedux: (value) => dispatch({type: actionType.CITY_CODE_VALUE, value}),
articleIdValueRedux: (value) => dispatch({type: actionType.ARTICLE_ID_VALUE, value})
};
};
export default connect(mapStateToProps, mapDispatchToProps)(SearchArticle);

You should still return null; as a safe clause just in case your condition doesn't match.
displayName = () => {
if(this.state.cityCodeval === 'nyc' && this.state.idVal === '1') {
console.log(this.state.cityCodeval); // console it here
console.log(this.state.idVal); // console it here
return (
<div>
<p>author name: {this.state.authorNameValue}</p>
<p>article text: {this.state.storyTextValue}</p>
</div>
);
}
return null;
}
Also now, in your render method you can do this.
{this.state.flag && this.displayName()}
This means that if the flag variable is true, call displayName it then executes the function. If you first condition matches it will return that otherwise it will return null;
Previously in your current code if the flag variable was true and it executed the function displayName where the if condition didn't meet. This caused an error because it had nothing to return.

Indeterminate checkbox in React JSX

How do I render an indeterminate checkbox via JSX?
Here's what I've tried:
function ICB({what}) {
return <input type="checkbox"
checked={what === "checked"}
indeterminate={what === "indeterminate"} />;
}
However, indeterminate is not an attribute on the HTMLElement, but a property. How do I set properties from React / JSX?
Solution:
As most of the answers below use findDOMNode or string refs, both of which are no longer considered good practice in React, I've written a more modern implementation:
function ICB() {
const [state, setState] = React.useState(0);
const indetSetter = React.useCallback(el => {
if (el && state === 2) {
el.indeterminate = true;
}
}, [state]);
const advance = () => setState(prev => (prev + 1) % 3);
return <input type="checkbox"
checked={state === 1}
ref={indetSetter}
onClick={advance} />;
}
ReactDOM.render(<ICB />, document.getElementById("out"));
<div id="out"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.1/umd/react-dom.production.min.js"></script>

You can also use the ref function directly:
ReactDOM.render(
<label>
<input
type="checkbox"
ref={input => {
if (input) {
input.indeterminate = true;
}
}}
/>
{' '}
Un test
</label>,
document.getElementById('root')
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="root"></div>

I would probably create a composite component that encapsulates the necessary hooks to set or unset the checkbox's indeterminate property. It looks like you're using ES2015 syntax, so I'll use some of those features here.
class IndeterminateCheckbox extends React.Component {
componentDidMount() {
if (this.props.indeterminate === true) {
this._setIndeterminate(true);
}
}
componentDidUpdate(previousProps) {
if (previousProps.indeterminate !== this.props.indeterminate) {
this._setIndeterminate(this.props.indeterminate);
}
}
_setIndeterminate(indeterminate) {
const node = React.findDOMNode(this);
node.indeterminate = indeterminate;
}
render() {
const { indeterminate, type, ...props } = this.props;
return <input type="checkbox" {...props} />;
}
}
// elsewhere
render() {
return <IndeterminateCheckbox
checked={this.props.state === "checked"}
indeterminate={this.props.state === "indeterminate"} />
}
Working example: https://jsbin.com/hudemu/edit?js,output

You can use the componentDidMount step (which is invoked after the initial rendering) to set that property:
componentDidMount() {
React.findDOMNode(this).indeterminate = this.props.state === "indeterminate";
}
If you want that property to be updated with subsequent renders, do the same thing in componentDidUpdate also.

I'd suggest creating a simple component (code ported from coffeescript so mind you, might have some simple typos):
const React = require('react');
module.exports = class IndeterminateCheckbox extends React.Component {
componentDidMount() {
this.refs.box.indeterminate = this.props.indeterminate;
}
componentDidUpdate(prevProps, prevState) {
if(prevProps.indeterminate !== this.props.indeterminate) {
this.refs.box.indeterminate = this.props.indeterminate;
}
}
render() {
return <input {...this.props} ref="box" type="checkbox"/>;
}
}
Now you have a simple component that behaves exactly like a checkbox, that supports the indeterminate prop. Note there's plenty of room for improvements here, namely setting propTypes and proper defaults for some props, and of course implementing componentShouldUpdate to only do something when needed.

An alternative would be to use a ref attribute with a callback to set the property on the DOM node. For example:
render: function() {
return (
<input
type="checkbox"
ref={function(input) {
if (input != null) {
React.findDOMNode(input).indeterminate = this.props.indeterminate;
}}
{...this.props} />
)
}

Dont use React.findDOMNode(this).
It is risky.
export class SelectAll extends Component {
constructor(props) {
super(props);
this.state = {
checked: false
};
this.myRef = React.createRef();
this.onChange = this.onChange.bind(this);
this.update = this.update.bind(this);
}
onChange(e) {
const checked = e.target.checked;
this.setState({
checked: checked
});
this.selectAllNode.indeterminate = false;
}
update(state: {
checked: Boolean,
indeterminate: Boolean
}) {
this.setState({
checked: state.checked
});
this.myRef.current.indeterminate = state.indeterminate;
}
render() {
return ( <
input type = "checkbox"
name = "selectAll"
checked = {
this.state.checked
}
onChange = {
this.onChange
}
ref = {
this.myRef
}
/>
);
}
}

React v15 implementation:
import React from 'react';
export default class Checkbox extends React.Component {
componentDidMount() {
this.el.indeterminate = this.props.indeterminate;
}
componentDidUpdate(prevProps, prevState) {
if(prevProps.indeterminate !== this.props.indeterminate) {
this.el.indeterminate = this.props.indeterminate;
}
}
render() {
const {indeterminate, ...attrs} = this.props;
return <input ref={el => {this.el = el}} type="checkbox" {...attrs}/>;
}
}

Taken from my tutorial which shows how this works with the recent React features. I hope this helps someone who stumbles upon this older question:
const App = () => {
const [checked, setChecked] = React.useState(CHECKBOX_STATES.Empty);
const handleChange = () => {
let updatedChecked;
if (checked === CHECKBOX_STATES.Checked) {
updatedChecked = CHECKBOX_STATES.Empty;
} else if (checked === CHECKBOX_STATES.Empty) {
updatedChecked = CHECKBOX_STATES.Indeterminate;
} else if (checked === CHECKBOX_STATES.Indeterminate) {
updatedChecked = CHECKBOX_STATES.Checked;
}
setChecked(updatedChecked);
};
return (
<div>
<Checkbox
label="Value"
value={checked}
onChange={handleChange}
/>
<p>Is checked? {checked}</p>
</div>
);
};
const Checkbox = ({ label, value, onChange }) => {
const checkboxRef = React.useRef();
React.useEffect(() => {
if (value === CHECKBOX_STATES.Checked) {
checkboxRef.current.checked = true;
checkboxRef.current.indeterminate = false;
} else if (value === CHECKBOX_STATES.Empty) {
checkboxRef.current.checked = false;
checkboxRef.current.indeterminate = false;
} else if (value === CHECKBOX_STATES.Indeterminate) {
checkboxRef.current.checked = false;
checkboxRef.current.indeterminate = true;
}
}, [value]);
return (
<label>
<input ref={checkboxRef} type="checkbox" onChange={onChange} />
{label}
</label>
);
};