promises

const leadRepo = require('../lead/repository');

let dto = {
  email: req.body.email
};

leadRepo.findByEmail(dto.email).then( (doc) => {
    if(doc){
      res.status(200).end();
    }
    else{
      return leadRepo.add(dto);
    }
  })
  .then( lead => {
    res.status(201).json(lead);
  })
  .catch( (err) => {
    console.log(err);
    res.status(500).end();
  });