How does a parent component communicate with a child component that was passed in as a prop?

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10 Answers

communicatepassedparentchildcomponent
90%

The child component calls the parent callback function using props and passes the data to the parent component.,Pass the callback function to the child as a props from the parent component.,In the parent component, create a callback function. This callback function will retrieve the data from the child component.

Step 1: Create a React application using the following command:

npx create - react - app foldername

Step 2: After creating your project folder i.e. foldername, move to it using the following command:

cd foldername
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88%

From Parent to Child with Props,Then the Book component can receive and use those fields as contained in the props parameter to its function:,If the context value was a callback function, we could see this being used for child to parent communication as well.

1function BookList() {
2  const list = [
3    { title: 'A Christmas Carol', author: 'Charles Dickens' },
4    { title: 'The Mansion', author: 'Henry Van Dyke' },
5    // ...
6  ]
7
8  return (
9    <ul>
10      {list.map((book, i) => <Book title={book.title} author={book.author} key={i} />)}
11    </ul>
12  )
13}
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72%

As easy as passing data between React components seems, it can get a bit complex at times. Although passing data from parent to child and vice-versa is an upfront process, passing data to and from siblings requires specific tools that React and JavaScript provide.,If it seems a bit strange to you, take a look at the Zombie component after adjustment.,To keep it simple, the showMessage method will only display a message that contains the name of the zombie and the name of its attack.

1import React, { Component } from 'react';
2import './App.css';
3
4import GameMgr from './components/GameMgr';
5
6class App extends Component {
7  render() {
8    return (
9      <div className="App">
10        <GameMgr />
11      </div>
12    );
13  }
14}
15
16export default App;
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65%

Phew. Let's just write some code! We will write a method in the App component that receives a zipcode and saves it in it's own state.,Pretty easy. We have seen this. We know, though, that since we are changing state, we need to initialize our state in the constructor.,One last thing we need to do is make sure that we are initializing these new pieces of state in our constructor.

Phew. Let's just write some code! We will write a method in the App component that receives a zipcode and saves it in it's own state.

onFormSubmit(zipcode) {
   this.setState({
      zipcode
   });
}
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75%

When you need to pass data from a parent to child class component, you do this by using props.,Passing data from child to parent,Passing data from parent to child class components

 Pretag team - issue, fix, solve, resolve
40%

The simplest form of communication between components is via properties — usually called props. Props are the parameters passed into child components by parents, similar to arguments to a function.,Every React app is composed of interacting components. How these components communicate is an essential aspect of the UI architecture. As applications grow larger and more complex, component interaction becomes even more important., How to use React functional components

Listing 1. Props (class-based)

function App(){  return <div>    <AppChild name="Matt" />    </div>}function AppChild(props){  return <span>      My name is {props.name}    </span>}ReactDOM.render(<App />, document.getElementById('app'));
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22%

React is a JavaScript library created by Facebook. Data handling in React could be a bit tricky, but not as complicated as it might seem. I have currently compiled three methods of Data Handling in React :-,I hope this gives clear implementation details for Data Passing between various components in React.Recommended:,Your home for data science. A Medium publication sharing concepts, ideas and codes.

Let us consider our directory structure to be such that the Parent Component renders child components in the Application.

App└── Parent├── Child1└── Child2
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60%

Downward communication is the communication between a parent and a child component done by the so-called props, which are a kind of “user input.”,Upon opening your devtools, you can see that you can access the input data from the child component to the parent component.,It’s just working fine, but there’s still no communication between this child and the parent. Let’s say we would like, for instance, to console.log() user input in the parent component.

import React from "react";
import ReactDOM from "react-dom";
import App from "./app";

ReactDOM.render(
<App />, document.getElementById("root"));
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48%

The webpack.config.js file has an entry object. This object is used to specify the input file which will be used to define all components of the application. , The devServer object defines the port on which the application is hosted. , The output object defines the output file generated based on all components in the application and various module loaders.

npm init - y
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23%

This should work. While sending the prop back you are sending that as an object rather send that as a value or alternatively use it as an object in the parent component. Secondly you need to format your json object to contain name value pairs and use valueField and textField attribute of DropdownList,What I need is to get the selected value by user in the parent component. I'm getting this error:,In the ChildComponent, update the data using the received function through prop to send the data back to ParentComponent.

Parent:

<div className="col-sm-9">
     <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
</div>

Child:

handleLangChange = () => {
   var lang = this.dropdown.value;
   this.props.onSelectLanguage(lang);
}

Parent

class ParentComponent extends React.Component {

    state = { language: '' }

    handleLanguage = (langValue) => {
        this.setState({language: langValue});
    }

    render() {
         return (
                <div className="col-sm-9">
                    <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
                </div>
        )
     }
}

Child

var json = require("json!../languages.json");
var jsonArray = json.languages;

export class SelectLanguage extends React.Component {
    state = {
            selectedCode: '',
            selectedLanguage: jsonArray[0],
        }

    handleLangChange = () => {
        var lang = this.dropdown.value;
        this.props.onSelectLanguage(lang);            
    }

    render() {
        return (
            <div>
                <DropdownList ref={(ref) => this.dropdown = ref}
                    data={jsonArray} 
                    valueField='lang' textField='lang'
                    caseSensitive={false} 
                    minLength={3}
                    filter='contains'
                    onChange={this.handleLangChange} />
            </div>            
        );
    }
}

Using createClass syntax which the OP used in his answer Parent

const ParentComponent = React.createClass({
    getInitialState() {
        return {
            language: '',
        };
    },

    handleLanguage: function(langValue) {
        this.setState({language: langValue});
    },

    render() {
         return (
                <div className="col-sm-9">
                    <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
                </div>
        );
});

Child

var json = require("json!../languages.json");
var jsonArray = json.languages;

export const SelectLanguage = React.createClass({
    getInitialState: function() {
        return {
            selectedCode: '',
            selectedLanguage: jsonArray[0],
        };
    },

    handleLangChange: function () {
        var lang = this.refs.dropdown.value;
        this.props.onSelectLanguage(lang);            
    },

    render() {

        return (
            <div>
                <DropdownList ref='dropdown'
                    data={jsonArray} 
                    valueField='lang' textField='lang'
                    caseSensitive={false} 
                    minLength={3}
                    filter='contains'
                    onChange={this.handleLangChange} />
            </div>            
        );
    }
});

JSON:

{
   "languages": [

      {
         "code": "aaa",
         "lang": "english"
      },
      {
         "code": "aab",
         "lang": "Swedish"
      },
   ]
}
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