import React, { Component } from 'react';

class SearchBar extends Component {
  render(){
    return <input onChange={ event => console.log(event.target.value)} />;
  }
}

export default SearchBar;

import React, { Component } from 'react';

class SearchBar extends Component {
  constructor(props) {
    super(props);

    this.state = { term: ''};
  }
  render(){
    return (
      <div>
        <input onChange={ event => this.setState({ term: event.target.value })} />
        Value of the input: {this.state.term}
      </div>
      );
  }
}

export default SearchBar;

Initialize and set state best example