Cleaner code in NodeJs with async-await - Mongoose calls example
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A lot has been written already about the transition from callbacks
to promises and now to the new
async/await1 feature in ES7.
"The purpose of `async/await` functions is to simplify the behavior of using promises synchronously and to perform some behavior on a group of `Promises`. Just as `Promises` are similar to structured callbacks, `async/await is similar to combining generators and promises."[^1]
In this blog post I present what this code “upgrade” meant for CRUD operations performed on codingmarks. I use Moongoose in an ExpressJS/NodeJS backend to perform the operations against a MongoDB database.
Create
Before
router.post('/:id/bookmarks', keycloak.protect(), function(req, res, next){
const descriptionHtml = req.body.descriptionHtml ? req.body.descriptionHtml: converter.makeHtml(req.body.description);
console.log(req.body);
var bookmark = new Bookmark({
name: req.body.name,
location: req.body.location,
language: req.body.language,
description: req.body.description,
descriptionHtml: descriptionHtml,
category: req.body.category,
tags: req.body.tags,
publishedOn: req.body.publishedOn,
githubURL: req.body.githubURL,
userId: req.params.id,
shared: req.body.shared,
starredBy: req.body.starredBy
});
console.log('Bookmark to create ' + bookmark);
bookmark.save(function (err, updatedBookmark) {
if (err){
if(err.name == 'ValidationError'){
var errorMessages = [];
for (var i in err.errors) {
errorMessages.push(err.errors[i].message);
}
var error = new Error('Validation MyError', errorMessages);
console.log(JSON.stringify(error));
res.setHeader('Content-Type', 'application/json');
return res.status(409).send(JSON.stringify(new MyError('Validation Error', errorMessages)));
}
console.log(err);
res.status(500).send(err);
} else {
res.set('Location', 'http://localhost:3000/' + req.params.id + '/bookmarks/' + updatedBookmark.id);
res.status(201).send({response:'Bookmark created for userId ' + req.params.id});
}
// saved!
});
});
After
router.post('/:id/bookmarks', keycloak.protect(), async (req, res) => {
const descriptionHtml = req.body.descriptionHtml ? req.body.descriptionHtml: converter.makeHtml(req.body.description);
const bookmark = new Bookmark({
name: req.body.name,
location: req.body.location,
language: req.body.language,
description: req.body.description,
descriptionHtml: descriptionHtml,
category: req.body.category,
tags: req.body.tags,
publishedOn: req.body.publishedOn,
githubURL: req.body.githubURL,
userId: req.params.id,
shared: req.body.shared,
starredBy: req.body.starredBy
});
try{
let newBookmark = await bookmark.save();
res.set('Location', 'http://localhost:3000/' + req.params.id + '/bookmarks/' + newBookmark.id);
res.status(201).send({response:'Bookmark created for userId ' + req.params.id});
} catch (err){
if (err.name === 'MongoError' && err.code === 11000) {
res.status(409).send(new MyError('Duplicate key', [err.message]));
}
res.status(500).send(err);
}
});Read
Before
/* GET bookmarks for user */
router.get('/:id/bookmarks', keycloak.protect(), function(req, res, next) {
if(req.query.term){
var regExpTerm = new RegExp(req.query.term, 'i');
var regExpSearch=[{name:{$regex:regExpTerm}}, {description:{$regex: regExpTerm }}, {category:{$regex:regExpTerm }}, {tags:{$regex:regExpTerm}}];
Bookmark.find({userId:req.params.id, '$or':regExpSearch}, function(err, bookmarks){
if(err){
return res.status(500).send(err);
}
res.send(bookmarks);
});
} else {//no filter - all bookmarks
Bookmark.find({userId:req.params.id}, function(err, bookmarks){
if(err){
return res.status(500).send(err);
}
res.send(bookmarks);
});
}
});
After
/* GET bookmarks for user */
router.get('/:id/bookmarks', keycloak.protect(), async (req, res) => {
try{
let bookmarks;
if(req.query.term){
var regExpTerm = new RegExp(req.query.term, 'i');
var regExpSearch=[{name:{$regex:regExpTerm}}, {description:{$regex: regExpTerm }}, {category:{$regex:regExpTerm }}, {tags:{$regex:regExpTerm}}];
bookmarks = await Bookmark.find({userId:req.params.id, '$or':regExpSearch});
} else {//no filter - all bookmarks
bookmarks = await Bookmark.find({userId:req.params.id});
}
res.send(bookmarks);
} catch (err) {
return res.status(500).send(err);
}
});Update
Before
/**
* full UPDATE via PUT - that is the whole document is required and will be updated
* the descriptionHtml parameter is only set in backend, if only does not come front-end (might be an API call)
*/
router.put('/:userId/bookmarks/:bookmarkId', keycloak.protect(), function(req, res, next) {
if(!req.body.descriptionHtml){
req.body.descriptionHtml = converter.makeHtml(req.body.description);
}
Bookmark.findOneAndUpdate({_id: req.params.bookmarkId, userId: req.params.userId}, req.body, {new: true}, function(err, bookmark){
if(err){
if (err.name === 'MongoError' && err.code === 11000) {
res.status(409).send(new MyError('Duplicate key', [err.message]));
}
res.status(500).send(new MyError('Unknown Server Error', ['Unknow server error when updating bookmark for user id ' + req.params.userId + ' and bookmark id '+ req.params.bookmarkId]));
}
if(!bookmark){
return res.status(404).send('Bookmark not found for user');
}
res.status(200).send(bookmark);
});
});
After
/**
* full UPDATE via PUT - that is the whole document is required and will be updated
* the descriptionHtml parameter is only set in backend, if only does not come front-end (might be an API call)
*/
router.put('/:userId/bookmarks/:bookmarkId', keycloak.protect(), async (req, res) => {
if(!req.body.descriptionHtml){
req.body.descriptionHtml = converter.makeHtml(req.body.description);
}
try {
let bookmark = await Bookmark.findOneAndUpdate({_id: req.params.bookmarkId, userId: req.params.userId}, req.body, {new: true});
if (!bookmark) {
return res.status(404).send(new MyError('Not Found Error', ['Bookmark for user id ' + req.params.userId + ' and bookmark id '+ req.params.bookmarkId + ' not found']));
} else {
res.status(200).send(bookmark);
}
} catch (err) {
if (err.name === 'MongoError' && err.code === 11000) {
res.status(409).send(new MyError('Duplicate key', [err.message]));
}
res.status(500).send(new MyError('Unknown Server Error', ['Unknow server error when updating bookmark for user id ' + req.params.userId + ' and bookmark id '+ req.params.bookmarkId]));
}
});Delete
Before
/*
* DELETE bookmark for user
*/
router.delete('/:userId/bookmarks/:bookmarkId', keycloak.protect(), function(req, res, next) {
Bookmark.findOneAndRemove({_id: req.params.bookmarkId, userId: req.params.userId}, function(err, bookmark){
if(err){
return res.status(500).send(new MyError('Unknown server error', ['Unknown server error when trying to delete bookmark with id ' + req.params.bookmarkId]));
}
if(!bookmark){
return res.status(404).send(new MyError('Not Found Error', ['Bookmark for user id ' + req.params.userId + ' and bookmark id '+ req.params.bookmarkId + ' not found']));
}
res.status(204).send('Bookmark successfully deleted');
});
});
After
/*
* DELETE bookmark for user`
*/
router.delete('/:userId/bookmarks/:bookmarkId', keycloak.protect(), async (req, res) => {
try {
let bookmark = await Bookmark.findOneAndRemove({_id: req.params.bookmarkId, userId: req.params.userId});
if (!bookmark) {
return res.status(404).send(new MyError('Not Found Error', ['Bookmark for user id ' + req.params.userId + ' and bookmark id '+ req.params.bookmarkId + ' not found']));
} else {
res.status(204).send('Bookmark successfully deleted');
}
} catch (err) {
return res.status(500).send(new MyError('Unknown server error', ['Unknown server error when trying to delete bookmark with id ' + req.params.bookmarkId]));
}
});Note how the code has become shorter, easier to read (especially for someone like me, with a Java/JavaEE background) and the error handling is now much clearer.
Another cool feature of async/await is how to easily implement multiple parallel, but that in a coming post…
Source code for codingmarks.org is available on Github - frontend and backend.
