[javascript] How to update parent's state in React?

My structure looks as follows:

Component 1  

 - |- Component 2


 - - |- Component 4


 - - -  |- Component 5  

Component 3

Component 3 should display some data depending on state of Component 5. Since props are immutable, I can't simply save it's state in Component 1 and forward it, right? And yes, I've read about redux, but don't want to use it. I hope that it's possible to solve it just with react. Am I wrong?

It seems that we can only pass data from parent to child as react promotes Unidirectional Data Flow, but to make parent update itself when something happens in its "child component", we generally use what is called a "callback function".

We pass the function defined in the parent to the child as "props" and call that function from the child triggering it in the parent component.

class Parent extends React.Component {
  handler = (Value_Passed_From_SubChild) => {
    console.log("Parent got triggered when a grandchild button was clicked");
    console.log("Parent->Child->SubChild");
    console.log(Value_Passed_From_SubChild);
  }
  render() {
    return <Child handler = {this.handler} />
  }
}
class Child extends React.Component {
  render() {
    return <SubChild handler = {this.props.handler}/ >
  }
}
class SubChild extends React.Component { 
  constructor(props){
   super(props);
   this.state = {
      somethingImp : [1,2,3,4]
   }
  }
  render() {
     return <button onClick = {this.props.handler(this.state.somethingImp)}>Clickme<button/>
  }
}
React.render(<Parent />,document.getElementById('app'));

 HTML
 ----
 <div id="app"></div>

In this example we can make data pass from SubChild -> Child -> Parent by passing function to its direct Child.

If this same scenario is not spread everywhere you can use React's context, specially if you don't want to introduce all the overhead that state management libraries introduce. Plus, it's easier to learn. But be careful, you could overuse it and start writing bad code. Basically you define a Container component (that will hold and keep that piece of state for you) making all the components interested in writing/reading that piece of data its children (not necessarily direct children)

https://reactjs.org/docs/context.html

You could also use plain React properly instead.

<Component5 onSomethingHappenedIn5={this.props.doSomethingAbout5} />

pass doSomethingAbout5 up to Component 1

    <Component1>
        <Component2 onSomethingHappenedIn5={somethingAbout5 => this.setState({somethingAbout5})}/>
        <Component5 propThatDependsOn5={this.state.somethingAbout5}/>
    <Component1/>

If this a common problem you should starting thinking moving the whole state of the application to someplace else. You have a few options, the most common are:

https://redux.js.org/

https://facebook.github.io/flux/

Basically, instead of managing the application state in your component you send commands when something happens to get the state updated. Components pull the state from this container as well so all the data is centralized. This doesn't mean can't use local state anymore, but that's a more advanced topic.

As per your question, I understand that you need to display some conditional data in Component 3 which is based on state of Component 5. Approach :

1. State of Component 3 will hold a variable to check whether Component 5's state has that data
2. Arrow Function which will change Component 3's state variable.
3. Passing arrow function to Component 5 with props.
4. Component 5 has an arrow function which will change Component 3's state variable
5. Arrow function of Component 5 called on loading itself

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
Class Component3 extends React.Component {
    state = {
        someData = true
    }

    checkForData = (result) => {
        this.setState({someData : result})
    }

    render() {
        if(this.state.someData) {
            return(
                <Component5 hasData = {this.checkForData} />
                //Other Data
            );
        }
        else {
            return(
                //Other Data
            );
        }
    }
}

export default Component3;

class Component5 extends React.Component {
    state = {
        dataValue = "XYZ"
    }
    checkForData = () => {
        if(this.state.dataValue === "XYZ") {
            this.props.hasData(true);
        }
        else {
            this.props.hasData(false);
        }
    }
    render() {
        return(
            <div onLoad = {this.checkForData}>
                //Conditional Data
            </div>
        );
    }
}
export default Component5;

-We can create ParentComponent and with handleInputChange method to update the ParentComponent state. Import the ChildComponent and we pass two props from parent to child component ie.handleInputChange function and count.

import React, { Component } from 'react';
import ChildComponent from './ChildComponent';

class ParentComponent extends Component {
  constructor(props) {
    super(props);
    this.handleInputChange = this.handleInputChange.bind(this);
    this.state = {
      count: '',
    };
  }

  handleInputChange(e) {
    const { value, name } = e.target;
    this.setState({ [name]: value });
  }

  render() {
    const { count } = this.state;
    return (
      <ChildComponent count={count} handleInputChange={this.handleInputChange} />
    );
  }
}

• Now we create the ChildComponent file and save as ChildComponent.jsx. This component is stateless because the child component doesn't have a state. We use the prop-types library for props type checking.

  import React from 'react';
  import { func, number } from 'prop-types';
  
  const ChildComponent = ({ handleInputChange, count }) => (
    <input onChange={handleInputChange} value={count} name="count" />
  );
  
  ChildComponent.propTypes = {
    count: number,
    handleInputChange: func.isRequired,
  };
  
  ChildComponent.defaultProps = {
    count: 0,
  };
  
  export default ChildComponent;
  

<Footer 
  action={()=>this.setState({showChart: true})}
/>

<footer className="row">
    <button type="button" onClick={this.props.action}>Edit</button>
  {console.log(this.props)}
</footer>

Try this example to write inline setState, it avoids creating another function.

I've used a top rated answer from this page many times, but while learning React, i've found a better way to do that, without binding and without inline function inside props.

Just look here:

class Parent extends React.Component {

  constructor() {
    super();
    this.state={
      someVar: value
    }
  }

  handleChange=(someValue)=>{
    this.setState({someVar: someValue})
  }

  render() {
    return <Child handler={this.handleChange} />
  }

}

export const Child = ({handler}) => {
  return <Button onClick={handler} />
}

The key is in an arrow function:

handleChange=(someValue)=>{
  this.setState({someVar: someValue})
}

You can read more here. Hope this will be useful for somebody =)

I found the following working solution to pass onClick function argument from child to the parent component:

Version with passing a method()

//ChildB component
class ChildB extends React.Component {

    render() {

        var handleToUpdate  =   this.props.handleToUpdate;
        return (<div><button onClick={() => handleToUpdate('someVar')}>
            Push me
          </button>
        </div>)
    }
}

//ParentA component
class ParentA extends React.Component {

    constructor(props) {
        super(props);
        var handleToUpdate  = this.handleToUpdate.bind(this);
        var arg1 = '';
    }

    handleToUpdate(someArg){
            alert('We pass argument from Child to Parent: ' + someArg);
            this.setState({arg1:someArg});
    }

    render() {
        var handleToUpdate  =   this.handleToUpdate;

        return (<div>
                    <ChildB handleToUpdate = {handleToUpdate.bind(this)} /></div>)
    }
}

if(document.querySelector("#demo")){
    ReactDOM.render(
        <ParentA />,
        document.querySelector("#demo")
    );
}

Look at JSFIDDLE

Version with passing an Arrow function

//ChildB component
class ChildB extends React.Component {

    render() {

        var handleToUpdate  =   this.props.handleToUpdate;
        return (<div>
          <button onClick={() => handleToUpdate('someVar')}>
            Push me
          </button>
        </div>)
    }
}

//ParentA component
class ParentA extends React.Component { 
    constructor(props) {
        super(props);
    }

    handleToUpdate = (someArg) => {
            alert('We pass argument from Child to Parent: ' + someArg);
    }

    render() {
        return (<div>
            <ChildB handleToUpdate = {this.handleToUpdate} /></div>)
    }
}

if(document.querySelector("#demo")){
    ReactDOM.render(
        <ParentA />,
        document.querySelector("#demo")
    );
}

Look at JSFIDDLE

This the way I do it.

type ParentProps = {}
type ParentState = { someValue: number }
class Parent extends React.Component<ParentProps, ParentState> {
    constructor(props: ParentProps) {
        super(props)
        this.state = { someValue: 0 }

        this.handleChange = this.handleChange.bind(this)
    }

    handleChange(value: number) {
        this.setState({...this.state, someValue: value})
    }

    render() {
        return <div>
            <Child changeFunction={this.handleChange} defaultValue={this.state.someValue} />
            <p>Value: {this.state.someValue}</p>
        </div>
    }
}

type ChildProps = { defaultValue: number, changeFunction: (value: number) => void}
type ChildState = { anotherValue: number }
class Child extends React.Component<ChildProps, ChildState> {
    constructor(props: ChildProps) {
        super(props)
        this.state = { anotherValue: this.props.defaultValue }

        this.handleChange = this.handleChange.bind(this)
    }

    handleChange(value: number) {
        this.setState({...this.state, anotherValue: value})
        this.props.changeFunction(value)
    }

    render() {
        return <div>
            <input onChange={event => this.handleChange(Number(event.target.value))} type='number' value={this.state.anotherValue}/>
        </div>
    }
}

I want to thank the most upvoted answer for giving me the idea of my own problem basically the variation of it with arrow function and passing param from child component:

 class Parent extends React.Component {
  constructor(props) {
    super(props)
    // without bind, replaced by arrow func below
  }

  handler = (val) => {
    this.setState({
      someVar: val
    })
  }

  render() {
    return <Child handler = {this.handler} />
  }
}

class Child extends React.Component {
  render() {
    return <Button onClick = {() => this.props.handler('the passing value')}/ >
  }
}

Hope it helps someone.

We can set parent state from child component by passing function into child component as props as below

class Parent extends React.Component{
    state = { term : ''}

     onInputChange = (event)=>{
         this.setState({term: event.target.value});
     }

     onFormSubmit= (event)=>{
         event.preventDefault();
         this.props.onFormSubmit(this.state.term);
     }

     render(){
         return (
             <Child onInputChange={this.onInputChange} onFormSubmit= 
                {this.onFormSubmit} />
         )
     }
}

   
class Child extends React.Component{

     render(){
        return (
             <div className="search-bar ui segment">
                 <form className="ui form" onSubmit={this.props.onFormSubmit}>
                    <div class="field">
                      <label>Search Video</label>
                      <input type="text" value={this.state.term} onChange= 
                           {this.props.onInputChange} />
                    </div>
                    
                 </form>
             </div>
         )
     }
}

This way child will update parent state onInputChange and onFormSubmit are props passed from parents. This can be called as and event Listeners in Child,hence state will get updated there

When ever you require to communicate between child to parent at any level down, then it's better to make use of context. In parent component define the context that can be invoked by the child such as

In parent component in your case component 3

static childContextTypes = {
        parentMethod: React.PropTypes.func.isRequired
      };

       getChildContext() {
        return {
          parentMethod: (parameter_from_child) => this.parentMethod(parameter_from_child)
        };
      }

parentMethod(parameter_from_child){
// update the state with parameter_from_child
}

Now in child component (component 5 in your case) , just tell this component that it want to use context of its parent.

 static contextTypes = {
       parentMethod: React.PropTypes.func.isRequired
     };
render(){
    return(
      <TouchableHighlight
        onPress={() =>this.context.parentMethod(new_state_value)}
         underlayColor='gray' >   

            <Text> update state in parent component </Text>              

      </TouchableHighlight>
)}

you can find Demo project at repo

This is how we can do it with the new useState hook. Method - Pass the state changer function as a props to the child component and do whatever you want to do with the function

import React, {useState} from 'react';

const ParentComponent = () => {
  const[state, setState]=useState('');
  
  return(
    <ChildConmponent stateChanger={setState} />
  )
}


const ChildConmponent = ({stateChanger, ...rest}) => {
  return(
    <button onClick={() => stateChanger('New data')}></button>
  )
}

Most of the answers given above are for React.Component based designs. If your are using useState in the recent upgrades of React library, then follow this answer

I found the following working solution to pass onClick function argument from child to the parent component with param:

parent class :

class Parent extends React.Component {
constructor(props) {
    super(props)

    // Bind the this context to the handler function
    this.handler = this.handler.bind(this);

    // Set some state
    this.state = {
        messageShown: false
    };
}

// This method will be sent to the child component
handler(param1) {
console.log(param1);
    this.setState({
        messageShown: true
    });
}

// Render the child component and set the action property with the handler as value
render() {
    return <Child action={this.handler} />
}}

child class :

class Child extends React.Component {
render() {
    return (
        <div>
            {/* The button will execute the handler function set by the parent component */}
            <Button onClick={this.props.action.bind(this,param1)} />
        </div>
    )
} }

I like the answer regarding passing functions around, its a very handy technique.

On the flip side you can also achieve this using pub/sub or using a variant, a dispatcher, as Flux does. The theory is super simple, have component 5 dispatch a message which component 3 is listening for. Component 3 then updates its state which triggers the re-render. This requires stateful components, which, depending on your viewpoint, may or may not be an anti-pattern. I'm against them personally and would rather that something else is listening for dispatches and changes state from the very top-down (Redux does this, but adds additional terminology).

import { Dispatcher } from flux
import { Component } from React

const dispatcher = new Dispatcher()

// Component 3
// Some methods, such as constructor, omitted for brevity
class StatefulParent extends Component {
  state = {
    text: 'foo'
  } 

  componentDidMount() {
    dispatcher.register( dispatch => {
      if ( dispatch.type === 'change' ) {
        this.setState({ text: 'bar' })
      }
    }
  }

  render() {
    return <h1>{ this.state.text }</h1>
  }
}

// Click handler
const onClick = event => {
  dispatcher.dispatch({
    type: 'change'
  })
}

// Component 5 in your example
const StatelessChild = props => {
  return <button onClick={ onClick }>Click me</button> 
}

The dispatcher bundles with Flux is very simple, it simply registers callbacks and invokes them when any dispatch occurs, passing through the contents on the dispatch (in the above terse example there is no payload with the dispatch, simply a message id). You could adapt this to traditional pub/sub (e.g. using the EventEmitter from events, or some other version) very easily if that makes more sense to you.

so, if you want to update parent component,

 class ParentComponent extends React.Component {
        constructor(props){
            super(props);
            this.state = {
               page:0
            }
        }

        handler(val){
            console.log(val) // 1
        }

        render(){
          return (
              <ChildComponent onChange={this.handler} />
           )
       }
   }


class ChildComponent extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
             page:1
        };
    }

    someMethod = (page) => {
        this.setState({ page: page });
        this.props.onChange(page)
    }

    render() {
        return (
       <Button
            onClick={() => this.someMethod()} 
       > Click
        </Button>
      )
   }
}

Here onChange is an attribute with "handler" method bound to it's instance. we passed the method handler to the Child class component, to receive via onChange property in its props argument.

The attribute onChange will be set in a props object like this:

props ={
onChange : this.handler
}

and passed to the child component

So the Child component can access the value of name in the props object like this props.onChange

Its done through the use of render props.

Now the Child component has a button “Click” with an onclick event set to call the handler method passed to it via onChnge in its props argument object. So now this.props.onChange in Child holds the output method in the Parent class Reference and credits: Bits and Pieces