Node.js v4.0.0 is here!

So we lived to see it. Node.js version 4 is here which means we have the latest V8, ES6 support and the latest security patches for our favorite tool! Well the previous statement cannot describe how much good things just happened. From the creation of Node.js, through the fork of IO.js, until finally the latest version and the merger happened and now the community has the word how Node.js will be shaped from now on.

I am personally very excited about that and I am currently going to test and update one of my Docker apps that installs and uses Node.js through NVM.

I am also expecting a lot of work on this major version and the patches and new features are coming sooner than later which makes it very interesting to use Node.js these days!

Enjoy!

Using requestIdleCallback — Google Web Updates

requestIdleCallback is new performance API for scheduling work when the user is idle.

Source: Using requestIdleCallback — Google Web Updates

Another functionality from Google Chrome that can make our JavaScript execution faster with this already fast browser. As I say faster I mean that the user experience will be improved as this kind of functionality allows us to execute some heavy code while the user is idle: reading a block of text and not clicking at the time, etc. With feature detection you can implement that right now and I hope such things will be widely adopted.

JavaScript: from callback hell through then-hell to generators+promises

Lately I’ve been refactoring and then refactoring and then some one of my JS apps every time I find a better way to handle the asynchronicity of the language. The app is a MEAN stack app but I am working mostly on the back-end built for Node.js with the intention to do the same for the front-end when I am satisfied with the back-end code.

So I started writing a Node.js code using the callbacks everywhere even some of my custom functions(in other apps) were made to receive and call callbacks. I was very happy how the callbacks looked like and I was writing them as the second parameter of the functions without thinking: callAsync(params, function(err, data)) all the way!

However little by little I started to add new and more complicated features and the need to nest multiple callbacks did arise. Add to that the checking for error on every callback first line and the code started to be hard to read.

At some time I discovered Promises. I decided to use the bluebird Promises package. It follows the standard and also provides additional functions that at some time are really needed. I was in love and probably still am with the then-chaining, calling async functions, attaching then() to them, returning a new async call that provides a Promise and checking the result in the next then, adding a catch() function to handle any error in the promises chain and avoiding the need to check for an error in every then(). The code was beautiful again and no pyramid of doom existed anymore.

However Promises and then-chaining created a little overhead where every then() needs a callback function and also this callback doesn’t have access to variables in the previous callback – only the result from the previous promise call. There was a need to declare helper variables in the outer scope: the function where the Promise chain is.

Then I discovered generator functions. Their basic usage doesn’t show that you can use them in place of callbacks or Promises but the fact that yield can receive a Promise makes them very interesting. Of course there is a need of a wrapper function to call the generator’s .next() and check its .done status. I decided to use the co package for that.

After all of this the code I use is similar to this one:

co(function* () {

  let user = yield User.findOneAsync({ _id: 12345678 });
  console.log('user', user);

  let user2 = yield User.findOneAsync({ _id: 112233 });
  console.log('user2', user2);

}).catch(function (err) {
  console.error(err);
});

The code above will execute synchronously. Pretty cool, huh?
User.findOneAsync() returns a Promise. yield-ing a Promise will make this type of configuration to wait for the Promise to be resolved/rejected. The resolved Promise’s value will be assigned to the variable on the left(user/user2).

Now the next thing for me is to use ES7’s async functions. I can run ES6 and ES7 code with transpilers like Babel on the back and front-end.
Async functions’ syntax is similar to the one with the generator above without the need to use a wrapper function. I am thinking to wait a little before using them and keeping the code close to what is available natively in the latest Node.js/io.js which is ES5/ES6 syntax at least until the near future(next year?) when the ES7 will be finalized and ready to be used/implemented in the JS engines.

Enable full ES6 support in Node.js – dynamic transpiling with Babel

Finally I’ve decided to go beyond Promises with Node.js and started to look how can I write easily ES6 code today in my apps. I’ve had the option to use io.js which has a good ES6 support by default, starting Node.js with the Harmony flag was also an option. However if I wanted as full as possible ES6 support I had to use Babel. There are 2 options here: static compiling and deploy or dynamic compiling when the application is ran. Babel uses cache so only the changed files are recompiled.

First I had to install babel through npm:

npm install babel --save

It is recommended to install babel globally but I wanted to have it in the local packages for easy CI testing.

Then I added this little piece of code on the top of the main app.js which is the file used when the application is started with `node app.js`:

require("babel/register");

One downside is that the main (app.js) file must contain only ES5 code if the Node.js version you are using is not supporting the new syntax. However you can just create one bootstrap.js that registers babel and includes the app.js which then can contain ES6 code(and vice versa: app.js as the main one including bootstrap.js).

I wanted to have the ES6 support in the tests too and because I use grunt, mocha and istanbul I’ve added this configuration to the Gruntfile.js:

mocha_istanbul: {
    src: 'test/server/',
    options: {
        ...
        mochaOptions: ['--compilers=js:babel/register']
    }
}

That way the tests are running with transpiled files and if I have an ES6 syntax there I am good.

I also had to add/change some configuration in .jshintrc which I use in the tests and in my IDE:

“esnext” : true, //this allows ES6 syntax
“predef”: [“-Promise”] //this allows me to use a Promise lib like bluebird instead the default ES6 implementation

I also changed the JavaScript engine in my IDE (Webstorm) from EcmaScript 5.1 to ES6 to make it happy with the new syntax.

After that I started adding some fat arrow functions and the app/tests are working. It’s interesting how the new features sometimes need more than a basic change. For example the fat arrow functions behave different with this and my code for mongoose static functions that was using return this.somefunc() needed to be changed.

If you use istanbul with the configuration above you may notice that the coverage data shows ES5 code with the source map encoded at the bottom of the pages. There’s an unstable branch on istanbul’s GitHub page about source maps which means that we’ll soon have the coverage in ES6 for free! I’ll also be waiting for the Node.js and io.js to be merged and see what works without transpilers.

You-Dont-Know-JS/es6 & beyond at master · getify/You-Dont-Know-JS

You-Dont-Know-JS – A book series on JavaScript. @YDKJS on twitter.

Source: You-Dont-Know-JS/es6 & beyond at master · getify/You-Dont-Know-JS

A book on ES6. Completely free, hosted on GitHub in a Markdown format which means you just click links and read long and smart chapters!

Is ReactJS faster than AngularJS ? | blog.500tech.com

Short answer ? Nope.Long answer ? Inside.

Source: Is ReactJS faster than AngularJS ?

The author said it well:

ReactJS is a great framework which we at 500Tech use and love. There are many benefits to choosing ReactJS for your next project. “Speed” should not be one of them.

It is shown that one must know very well the framework and environment he uses to be able to write code that executes fast. This usually comes with months/years of getting the right experience/reading resources in your day job and while working with other devs as a whole.

Be sure to check the comments as they point the good things in both frameworks.

I personally will stick with Angular, getting ready for version 2 and will continue reading from different sources about it to get to know what makes it good and what makes it fast.

Web Design Degree Center – Choosing Your Javascript Framework | WebDesignDegreeCenter.org

Pick your JavaScript framework: Angular.js, Ember.js or Backbone.js.

They all have pros and cons and they all will do the job. They are constantly developed and even introduce breaking changes in new versions which means developers find the flows and anti-patterns in their frameworks and do it right in the next major version for the good of the language and the developers using the frameworks:
Continue reading

An Introduction to Functional JavaScript | sitepoint.com

M. David Green demonstrates how you can start thinking functionally in JavaScript, by refactoring some all-too-common imperative code to a functional style.

Source: An Introduction to Functional JavaScript

The article starts with an old classical way of doing things with JavaScript and the DOM. Things like global variables with generic names!

It is then translated to a more modern OOP that uses the IIFE, the strict directive, constructor function and its prototype.

And then we enter the world of functional JavaScript! I can’t remember well right now but the final solution reminds me of a design pattern.

One additional interesting thing in the examples is how the author uses string concatenation through arrays ([].join()) instead of “str1” + “str2” as this way is proved to be faster probably because the + operator is overloaded to work with multiple variable types or something else – just remember that string concatenation in JavaScript is slow.

There’s one other solution to the same problem in the comments which may be called one-liner and also the type of Clever Programming which happens when the code is short, fast and clever but a bit hard for beginners to read and understand fast. However using regex is a must for experienced developers which makes this solution also good.

Keep reading on the link above.