I speak JavaScript, translate, please!

While compilers compile from a higher-level language to a lower-level language, a transpiler or transcompiler acts more like a converter. It is a source-to-source compiler that translates code to run in a different interpreter.

Recently, there's been a real battle among new languages that are transpiled to JavaScript and can run in the browser. I used Google Dart for quite some time, and I must admit, I really loved the language features. The problem with nonstandardized languages is that they depend heavily on community adoption and the hype. Also, it's almost certain that they will never run natively within the browser. This is also the reason why I prefer standard JavaScript, and the JavaScript of the future using transpilers and polyfills.

Some people argue that transpilers introduce code that isn't very performant and, therefore, recommend that you do not use ECMAScript 6 and transpilers at all. I don't agree with this for many reasons. Usually, this is about performance in micro or even nanosecond areas where this often really does not matter for most applications.

I don't mean that performance doesn't matter, but performance always needs to be discussed within a context. If you're trying to optimize a loop within your application by reducing processing time from 10 microseconds to five microseconds where you'd never iterate over more than 100 items, then you're probably spending your time on the wrong things.

Also, a very important fact is that transpiled code is designed by people who understand micro performance optimization much better than I do, and I'm sure their code runs faster than mine. On top of this, a transpiler is probably also the right place where you'd want to do performance optimization because this code is automatically generated and you don't lose maintainability of your code through performance quirks.

I'd like to quote Donald Knuth here and say that premature optimization is the root of all evil. I really recommend that you read his paper on this topic (Donald Knuth, December 1974, Structured Programming with go to Statements). Just because the goto statements got banished from all modern programming languages, it doesn't mean this is less of a good read.

Later on in this chapter, you'll learn about tools that help you use transpilers easily within your project, and we'll take a look at the decisions and directions Angular went with regarding their source code.

Let's look at a few language features that come with ECMAScript 6 and make our life much easier.