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Add to SafariWhen comparing TypeScript vs Reason ML, 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 Reason ML is ranked 10th. 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
Question 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 Uses the excellent Bucklescript Ocaml to Javascript transpiler
Pro Superior type inference
Ocaml type inference is so smart that you never have to repeat yourself and keep code very clean, type errors also are very pleasant.
Pro Aims to make the transition from Javascript easier
Despite being a completely different language Javascript programmer will find that the syntax of ReasonML has many familiarities with Javascript.
Pro Uses established compiler technology from Ocaml with a tweaked syntax that leans more towards Javascript
Pro Removes JavaScript "bad parts" but sticks to it's design philosophy
unlike other js-targetting languages that are thought as a way to have a language that pleases community X run in a browser, reason is really designed with JavaScript community in mind. it removes the bad parts but keeps its syntax and its best design principles (from Scheme): simplicity, minimalism, and functions as building block.
Pro Immutability with escape hatches
reason includes true immutability, but it has escape hatches to let you use mutations in exceptional cases.
Pro Compiles to JavaScript or assembly (ocaml)
The same reasonml code can compile to js (eg. run on browsers or node.js, use any lib in npm), or compile to assembly thru ocaml (unless of course you load js externals), running on any device, with C-comparable (or better) performance.
Pro JSX syntax natively supported
Reason was created by the creator of react, for developers already using JSX to template web or native UIs this results very familiar.
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 A standard async syntax is pending
Async syntax is not standard across native/js projects and in both cases a bit awkward for non-ocaml devs. Currently this is reasonml most voted issue in their GitHub repo so hopefully, there's news soon.
Con Ecosystem is a mess
A wonderful language, but a user is required to use multiple different package managers for many things (esy, bsb, npm). Some standard templates from bsb (e.g. react-starter) are not installable out of the box.
