validate.js

isValidEmail(e) {
    /*
    * This regex SHOULD capture 99% of valid e-mails, but it is from StackOverflow
    * so I can't garuntee that. It works well in tests, but if it fails, lets switch
    * to a simple /@/ or use the MailGun API.
    */
    const emailRegex = /[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?/
    const emailFieldValue = e.target.value
    if (emailFieldValue.length == 0) {
      this.setState({ validEmail: null })
    } else {
      const valid = emailRegex.test(emailFieldValue);
      if (valid == true) {
        this.setState({ validEmail: true })
      } else {
        this.setState({ validEmail: false })
      }
    }
  }