When comparing TypeScript vs Scala.js, the Slant community recommends TypeScript for most people. In the question“What are the best languages that compile to JavaScript? ” TypeScript is ranked 1st while Scala.js is ranked 12th. The most important reason people chose TypeScript is:
Typescript has optional static typing with support for interfaces and generics, and intelligent type inference. It makes refactoring large codebases a breeze, and provides many more safeguards for creating stable code.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Optional static typing
Typescript has optional static typing with support for interfaces and generics, and intelligent type inference.
It makes refactoring large codebases a breeze, and provides many more safeguards for creating stable code.
Pro Strong typed language
Lot of benefits of it, you can read this.
Pro Strict superset of Javascript
Every existing Javascript program is already a valid TypeScript program giving it the best support for existing libraries, which is particularly useful if you need to integrate with an existing Javascript code base.
Pro First party Visual Studio support
As a Microsoft developed project, it has first party Visual Studio support that's on par with its C# support with features like syntax sensitive statement completion.
Pro Has a repository of high quality TypeScript type definitions for popular libraries
There are many ready to use and high quality TypeScript definitions for popular libraries including jquery, angular, bootstrap, d3, lodash and many-many more.
Pro Adds support for object-oriented programming
Typescript enables familiar object-oriented programming patterns: classes, inheritance, public/private methods and properties, et cetera.
Pro Polyfill for ES6 fat-arrow syntax
Typescript implements the fat arrow syntax, which always maintains the current context for this
and is a shorter/more convenient syntax than traditional function definition.
Pro Great support for React, integrated typed JSX parsing
Strongly typed react components, so UI "templating" automatically gains type safety.
Pro Great support for editors (Sublime, Code, Vim, IntelliJ...)
Pro Works well with existing Javascript code
Both can call Javascript code and be called by Javascript code. Making transitioning to the language very easy.
Pro Compiles to very native looking code
Compiles to simple looking Javascript making it easy to understand what is happening and learn the language (if you already know Javascript).
Pro Built and supported by Microsoft
Being built by Microsoft, TypeScript is much more likely than most other similar open-source projects to receive continued long-term support, good documentation, and a steady stream of development.
Pro Ability to do functional programming
Pro Clear roadmap
TypeScript has a clear and defined roadmap with rapid and constant releases.
Pro Low number of logical errors brought in by built-in type annotations
TypeScript's built-in type signatures allow developers to fully document interfaces and make sure that they will be correctly compiled. Therefore, cutting down on logical errors.
Pro Works well with Angular 2
Angular 2 is built using TypeScript and applications built using it can make use of that (or not).
Pro Type inference
Scala offers type inference, which, while giving the same safety as Java's type system, allows programmers to focus on the code itself, rather than on updating type annotations.
Pro Implements a mature language
In contrast to other options, Scala.js is a compiler plugin for an already existing and mature language: Scala.
As such, it benefits automatically from the existing compiler, from the language design choices made for Scala, which exists and is established in the industry since years.
Pro Easy, type-safe, interop with JavaScript
The JavaScript-interop of Scala.js is very direct and lightweight.
Pro The strength of Scala on the server
The strength of Scala (JVM) on the server can not be underestimated, and is probably superior to any other choice listed here (where applicable; many have no server-side equivalent).
Being able to use such a powerful language (and ecosystem) on the server AND on the client, and sharing code between the two, is a big advantage.
Pro Extensive standard libraries
Scala.js implements most of the Scala standard library and many parts of the Java one. Among others, it supports Scala's rich collection library.
Pro Dead-code elimination
Scala.js performs dead-code elimination out of the box (when running in the "fullOpts" mode).
Pro Multiparadigm
Scala supports both Functional and Object Oriented styles of programming. Beginners can learn both paradigms without having to learn a new language, and experts can switch between the two according to what best suits their needs at the time.
Pro Crossbuilding
Keeps your client and server sources in sync.
Pro Incremental compilation
Through SBT, Scala.js supports incremental compilation out of the box. That is: SBT automatically picks-up the changes (think "watch" in other tools) and only recompiles what is needed.
This makes the development cycle fast and very pleasant to work with.
Pro Excellent tooling (IDE) support
The same good and mature tooling that can be used for Scala can be used for Scala.js out of the box (code-completion, refactoring, immediate feedback, etc.).
Pro Immutable values
The immutable values make it perfect for working with concurrency.
Pro Macros
Because Scala.js is a plugin to the Scala compiler, the whole power of the Scala language is available at compile-time. Which includes macros. Very expressive things can be done, in a type-safe way, which are difficult or impossible in other languages.
Pro Simple build system compared to Javascript
While SBT is arguably not as simple as Maven, it beats the chaos of the JavaScript build ecosystem.
Cons
Con Too similar to Javascript
Presents some advantages compared to Javascript, but because it is designed to be a superset of Javascript, it means all the bad parts of Javascript are still present.
Con Type checking not enforced by default
You have to use compiler flags to make sure it catches flaws like usage of implicit any, etc.
Con Type inference coverage is incomplete
The default type when declaring and using a variable is any
. For example, the following should break but does not:
function add(a:number) { return a + 1 }
function addAB(a, b) {return add(a) + b}
addAB("this should break but doesn't :(", 100)
In order to avoid this, you have to declare type signatures for every variable or parameter or set the flag --noImplicityAny
when running the compiler.
Con Requires "this" for field access
Even in cases were there is no ambiguity, you still have to use "this.fieldName" instead of just "fieldName".
Con Syntax is too verbose
Con No support for dead code elimination
Typescript compiler does not remove dead code from generated file(s), you have to use external tools to remove unused code after compilation. This is harder to achieve, because Typescript compiler eliminated all type information.
Con No support for conditional compilation
There is no clean way to have debug and release builds compiled from the same source, where the release version removes all debugging tools and outputs from the generated file(s).
Con Awful error messages
Comparing to Elm or Rust for example, TypeScript's error messages won't say you very much. For example if you change method of interface which your class implements it won't say your class have incorrect implementation. Instead it'll show error in usage of instances of class. In some cases it can spoil hours of your work trying to figure out why your parameters are incorrect.
Con Technical debt
As consequence of not enforcing type checking.
Con No Java-like package structure
If you prefer a Java-like approach of partitioning your code into different packages, the module system of typescript will confuse you.
Con Small community
Con No option to declare that a function throws errors
Con Can be intimidating for beginners
Scala is an industrial language. It brings functional programming to the JVM. All books/tutorials cover friendly aspects of Scala, but there are corners of the language that one can wander into that are not friendly to beginners.
Con A complex language with a lot of incidental complexity that results in significant mental overhead
Con Combines OOP and functional programming for a hodge-podge paradigm
Its excellent mix of functional and OOP programming just like Python to use the tool best suited