Function 未定义 no-undef

Question

Hi I'm a beginner in jsx and I'm facing I'm sure a simple bug but I'm unable to solve it i've coded a simple delete function in my app js, and I'm stuck on this error.

here's my App.js file

 import React, { Component } from 'react'; import Essai from './Essai.js'; import AddEssai from './addEssai.js'; class App extends Component { state = { essais: [ {name: 'pek', age: 30, sexe: 'f', id:'1'}, {name: 'plop', age: 31, sexe: 'fh', id:'2'}, {name: 'pekkrure', age: 35, sexe: 'h', id:'3'} ] } deleteEssai = (id) =>{ console.log('fonction ok') } render() { return ( <div className="App"> <h1>My first react app</h1> <Essai essai ={this.state.essais}/> <AddEssai deleteEssai = {this.deleteEssai} addEssai = {this.addEssai} /> </div> ) }; } export default App;

And here's my component

 import React, { Component } from 'react'; const Essai = (props) => { //console.log(this.props.age) const { essai } = props; const essaiList = essai.map( essai => { return( <div className= "essai" key = {essai.id}> <div>Name: {essai.name} </div> <div>Age: {essai.age} </div> <div>sexe: {essai.sexe} </div> <button onClick = {() => {deleteEssai(essai.id)}}>DELETE</button> </div> ) }) return( <div className = "essaiList"> {essaiList}; </div> ) } export default Essai

I always get this error

./src/Essai.js Line 13:43: 'deleteEssai' is not defined no-undef

If someone could take a minute to guide me that would be very nice thank you!!!

Answer 1

Actually you are using deleteEssai in your child component, but never pass it as a prop to it , so it will throw an undefined error since there is no such a thing there. You just need to pass it as a prop to your child component.

Like this:

<Essai deleteEssai={this.deleteEssai} essai={this.state.essais}/>

And then you need to destructure in your child component as well.

const { essai, deleteEssai } = props;

Answer 2

2 things you should look at:

1. You are not passing the deleteEssai as a prop to this component <Essai /> in you <App /> .

import React, { Component } from 'react';
import Essai from './Essai.js';
import AddEssai from './addEssai.js';


class App extends Component {
  state = {
    essais : [
      {name : 'pek', age: 30, sexe : 'f', id:'1'},
      {name : 'plop', age: 31, sexe : 'fh', id:'2'},
      {name : 'pekkrure', age: 35, sexe : 'h', id:'3'}
    ]
  }

  deleteEssai = (id) =>{
    console.log('fonction ok')
  } 


  render() {
    return (
      <div className="App">
       <h1>My first react app</h1>

       {/*                              ->>> Pass here*/}
       <Essai essai={this.state.essais} deleteEssai={this.deleteEssai}/>
       <AddEssai deleteEssai = {this.deleteEssai} addEssai = {this.addEssai} />
      </div>
   )
    };
}

export default App;

2. Then in <Essai /> you use it from prop:

import React, { Component } from 'react';

const Essai = (props) => {

    //console.log(this.props.age)
    // Desctructure 'deleteEssai' from props
    const { essai, deleteEssai } = props;
    const essaiList = essai.map( essai => {
        return(
            <div className= "essai" key = {essai.id}>
                <div>Name: {essai.name} </div>
                <div>Age: {essai.age} </div>
                <div>sexe: {essai.sexe} </div>
                <button onClick = {() => {deleteEssai(essai.id)}}>DELETE</button>
            </div>
        )
    })
    return(
        <div className = "essaiList">
            {essaiList};
        </div> 
    )

}
export default Essai;