node.js api keep code dry - node.js

Question

I was wondering , what is the best practice to keep the code DRY when developing node.js api with database calls.
I seems like I'm having alot of repeated code.
For example, look at this:
app.get('/api/users_count', function (req,res) {
pool.connect(function(err, client, done) {
if(err) {
return console.error('error fetching client from pool', err);
}
client.query('SELECT count(*) FROM users;', function(err, result) {
done();
if(err) {
return console.error('error running query', err);
}
res.json({"users count": result.rows[0].count});
});
});
});
and this:
app.get('/api/users/:id', function (req,res) {
pool.connect(function(err, client, done) {
if(err) {
return console.error('error fetching client from pool', err);
}
client.query('SELECT name FROM users WHERE id=$1;',req.param.id, function(err, result) {
done();
if(err) {
return console.error('error running query', err);
}
res.json({"user name": result.rows[0].name});
});
});
});
How can I avoid the repeating of error handing , connect call, and just focus on route and query.
Thanks!

Answer 1

Take a look at sample below, should help
//Create fn that connects, pulls data, and passes it to callback
function customPool(query, values, callback) {
pool.connect(function(err, client, done) {
if(err)
return callback(err);
client.query(query, values, function(q_err, result) {
done();
if(q_err)
return callback(q_err);
callback(null, result.rows);
});
}
}
//Reuse it
app.get('/api/users_count', function (req,res) {
var query = 'SELECT count(*) FROM users;';
customPool(query, undefined, function(err, rows) {
if(err)
return console.error('error fetching client from pool', err);
res.json({"users count": rows[0].count});
});
});
app.get('/api/users/:id', function (req,res) {
var query = 'SELECT name FROM users WHERE id=$1;';
customPool(query, req.params.id, function(err, rows) { //<-- notice, req.params.id not req.param.id
if(err)
return console.error('error fetching client from pool', err);
res.json({"users name": rows[0].name});
});
});

Answer 2

For starters, use pg-promise for database communications, to avoid connecting manually. Then your code will be way simpler, as shown below.
code 1:
app.get('/api/users_count', function (req, res) {
db.one('SELECT count(*) FROM users')
.then(data=> {
res.json({"users count": +data.count});
})
.catch(error=> {
// should provide a response here also ;)
console.error(error);
});
});
code 2:
app.get('/api/users/:id', function (req, res) {
db.one('SELECT name FROM users WHERE id=$1', +req.param.id)
.then(user=> {
res.json({"user name": user.name});
})
.catch(error=> {
// should provide a response here also ;)
console.error(error);
});
});
Then you can simplify it further, by implementing a generic request->response logic, depending on your application's requirements.