error: invalid input syntax for integer: "{"email":"email@gmail.com","password":"hashedpasswordhere"}"

function User(){
  this.save = function(callback) {
  pool.connect();

  pool.query('INSERT INTO users(email, password) VALUES($1, $2) RETURNING *', [this.email, this.password], function (err, result) {
    if(err){
      console.log(err);
      return console.error('error running query', err);
    }
    var user = result.rows[0]
    console.log(user);
    return callback(user);
  });
  };
}

{ id: 1,
  email: 'email@gmail.com',
  password: 'hashedpasswordhere' }

User {
  save: [Function],
  email: 'email@gmail.com',
  password: 'hashedpasswordhere' }