vi src/ContactsList.js

import React from 'react';
import Contact from './Contact';
class ContactsList extends React.Component{
     constructor(){
        super();
        this.state ={
            search:''
        };
     }

     updateSearch(event){
        // console.log(event.target.value);
        this
 
.setState({search:event.target.value.substr(0,20)});

     }
    render(){
        let filteredContacts = this.props.contacts.filter(
            (contact) => {
                return contact.name.toLowerCase().indexOf(this.state.search.toLowerCase())!= -1;
            }
            );
         console.log(this
 
.props.contacts);

        return(
            <div>
            <input type="text" 
            value={this.state.search}
            onChange={this.updateSearch.bind(this)}
            />

            <ul>
            {filteredContacts.map((contact)=>{
                return <Contact  contact={contact} key={contact.id}/>
            })}


            </ul>

            </div>
            )
    }
}
export default
 
 ContactsList;