Call custom method on form submit redux form

//create a file submit.js and write method to call on form submit
import { SubmissionError } from 'redux-form';

const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));

function submitMethod(values) {
    return sleep(1200).then(() => { // simulate server latency
        if (!['alex', 'july'].includes(values.firstname)) {
            throw new SubmissionError({
                firstname: 'First name you entered is incorrect',
                _error: 'Not able to find First Name!',
            });
        } else {
            window.alert(`Submitted Object is :\n ${JSON.stringify(values, null, 2)}`);
        }
    });
}

export default submitMethod;

//create a file - MyValidationForm.js and design your form there to call above submitMethod in the form 
import React from 'react'
import { Field, reduxForm } from 'redux-form'
import submitMethod from './submit'

const renderThisInput = ({ input, label, type, meta: { touched, error } }) => (
  <div>
    <label>{label}</label>
    <div>
      <input {...input} placeholder={label} type={type} />
      {touched && error && <span>{error}</span>}
    </div>
  </div>
)

const MyValidationForm = props => {
  const { error, handleSubmit, pristine, reset, submitting } = props
  return (
    <form onSubmit={handleSubmit(submit)}> //Calling - submitMethod here from submit.js
      <Field
        name="firstname"
        type="text"
        component={renderThisInput}
        label="First Name"
      />
      <Field
        name="lastname"
        type="text"
        component={renderThisInput}
        label="Last Name"
      />
      {error && <strong>{error}</strong>}
      <div>
        <button type="submit" disabled={submitting}>
          Check Values
        </button>
        <button type="button" disabled={pristine || submitting} onClick={reset}>
          Rest Form
        </button>
      </div>
    </form>
  )
}

export default reduxForm({
  form: 'myValidationForm'
})(MyValidationForm)