how to add function on event onclick on array.map in react js

Question

class ProjectFirestoreData extends Component {
    constructor(props) {
        super(props);
        this.userDelete = this.userDelete.bind(this)
    }
    userDelete(authorId){
        console.log(authorId)
    }
    render() {
        let {firestore} = this.props;
        if(!Array.isArray(firestore) || !firestore.length ){
            return (
                    <div>
                        <h1>Loading</h1>
                    </div>
                )
        }
        else{
            return (
                    <div className="col-md-8">
                        <div className="row">
                            {
                                firestore.map(function(index, elem) {
                                    return (
                                        <div className="col-md-6 p-3" key={index.name}  >
                                            <div className="card">
                                              <img className="card-img-top" src="..." alt="Card" />
                                              <div className="card-body">
                                                <h5 className="card-title text-dark">AuthorName is :  {index.authorFirstName} </h5>
                                                <p className="card-text text-dark">Some quick example text to build on the card title and make up the bulk of the card's content.
                                                </p>
                                                <Link to={`/userdetails/${index.authorId}`} className="btn btn-primary">Show Full Data</Link>
                                                <button type="button" class="btn btn-dark" onClick={() => this.userDelete(index.authorId)}>Dark</button>
                                              </div>
                                            </div>
                                        </div>

                                        )
                                })
                            }


                        </div>
                    </div>
                )
        }
    }

}

onclick event is working after the array.map , but it is not working under the array.map is there any way of achieving it ? i have tried adding

<button type="button" class="btn btn-dark" onClick={() =>this.userDelete(index.authorId)}>Dark</button>

after array.map and it is working fine . but under array.map it is not working . the error says

TypeError: Cannot read property 'userDelete' of undefined

Answer 1

onclick event inside map:

 <div className={styles.file_content_show}>
                            {this.state.fileinformation.map((item)=>{ 
                                    return (
                                      
                                      <p className={styles.file_name_show}>{item.file_name}
                                      <span className={styles.file_size_date}> ({item.file_size} | {item.file_modified_date}) <img src={attachmentdelete_logo} className={styles.attachmentdelete_logo} onClick={this.deleteattachment.bind(item.file_size)}/></span>
                                      </p>
                                    );    
                                    
                                  })}
                                 
                                  
                                </div>

Function is this:

@autobind
private deleteattachment(file){
  var a=file;
}