React: setState onBlur

app.js

import React from 'react'

class App extends React.Component {
  state = { cep: '' }

  handleBlur = (e) => {
    this.setState({ cep: e.target.value })
  }

  render () {
    return (
      <React.Fragment>
        <input type='text' onBlur={this.handleBlur} />
        {this.state.cep && <span>CEP: {this.state.cep}</span>}
      </React.Fragment>
    )
  }
}