When comparing ClojureScript vs Idris, the Slant community recommends ClojureScript for most people. In the question“What are the best languages that compile to JavaScript? ” ClojureScript is ranked 6th while Idris is ranked 23rd. The most important reason people chose ClojureScript is:
Figwheel builds your ClojureScript code and hot loads it into the browser as you are coding! Every time you save your ClojureScript source file, the changes are sent to the browser so that you can see the effects of modifying your code in real time.
Specs
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Pros
Pro Live interactive programming with figwheel
Figwheel builds your ClojureScript code and hot loads it into the browser as you are coding! Every time you save your ClojureScript source file, the changes are sent to the browser so that you can see the effects of modifying your code in real time.
Pro Simple syntax
Lispness makes ClojureScript trivial to comprehend after an initial learning overhead.
Pro Easy to use existing JavaScript libraries
Clojure and ClojureScript are designed to be able to interact with their host. So the language by design makes it is easy to use existing JS libraries.
Pro Targets Google Closure-ready JavaScript for immense optimizations
Google's Closure Library converts regular JavaScript into a highly optimized form - including dead code analysis/elimination. It can even remove pieces of unused code from 3rd party libraries (eg, if you import jQuery but only use one function, Google Closure includes only that piece).
Pro Share application logic between browser and Clojure server
Clojure is also able to run web servers, so one can reap similar benefits to NodeJS in terms of sharing code between client and server.
Pro Can be used with React out of the box
Pro Excellent build tools
Both Leiningen and Boot are great build tools that manage code dependencies and deployment.
Pro Excellent tools for web development
ClojureScript has superb wrappers around React.js (see Reagent) that make building single-page apps a breeze. With figwheel, it's a web dev experience unlike any other -- hotloaded code, repl interaction, and instantly reflected changes make good development fun and fast. You can add things like Garden to make CSS-writing part of the same holistic experience and suddenly all development is a pleasant, smooth process.
Pro The Spec core library
From the creator of Clojure:
Spec is a new core library (Clojure 1.9 and Clojurescript) to support data and function specifications in Clojure.
Writing a spec should enable automatic: Validation, Error reporting, Destructuring, Instrumentation, Test-data generation and Generative test generation.
Pro Full dependent types
Idris not only has support for type classes, but is a fully dependently typed language, giving you the full power to statically verify your code.
Pro Domain driven design and type driven development
Because of full dependent types in Idris, the programmer can focus more on modelling the domain with types and waste less time fixing common bugs that the type checker will catch. Dependent types help apply type driven development and a lot of code auto generation, making the compiler and type checker an ally in developing working software instead of just getting in the way.
Cons
Con Tooling is horrible
I've never seen worse tooling before. Writing tests and getting test coverage reports is near impossible. Tooling is brittle and clunky. Feels prehistoric.
Con Syntax may seem cryptic to people not used to Lisp
Lisp is sometimes called "syntax-less" and this is bewildering to those steeped in Algol-type syntax (Java, Javascript, C, etc). Being a dialect of Lisp, ClojureScript's syntax may seem cryptic and hard to understand for people not used to it. While Lisp has very little syntax compared to other languages and it's generally considered pretty terse, there's still an initial overhead in learning the language.
Con Not widely used
Con Not widely used
Con Weaker type inference
As type inference is undecidable for dependently-typed languages, Idris cannot offer the full type inference that Haskell supports, and so more type annotations will be needed.
Con Different semantics from Haskell
Idris, while similar to Haskell, has strict semantics, which may cause some confusion if your backend is done in Haskell. If using Idris, it would make sense to do the backend in Idris as well, if not for the fact that Idris currently has fewer libraries available for web development than Haskell.