J vs ClojureScript
When comparing J vs ClojureScript, the Slant community recommends ClojureScript for most people. In the question“What is the best programming language to learn first?” ClojureScript is ranked 41st while J is ranked 47th. 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
Ranked in these QuestionsQuestion Ranking
Pros
Pro Every function is an operator
3 classes of operators (verbs, adverbs, and conjunctions) with verbs the most basic function that take either 1 or 2 (infix) parameters. Operators allow function composition with a minimum of parentheses.
Pro Simpler Imperative language constructs as failback to functional programming
J also supports multiline functional definitions similar to BASIC/Pascal. Including error handling.
Pro Compiled language speed from interpreted language.
Each built in operator is a C/asm function, and special code further optimizes some operator combinations. Result is optimized C speed from quick parsing. Array orientation parses and compiles a function once, and applies it to all array items.
Pro 25 year old language, with core unchanged in last 10 years
Still actively developed, but most recent changes have been in libraries and IDE and platform support.
Language is considered "perfected"... though not quite.
Pro Language reference has simple one page index
Complete core programming functional tools allow writting programs and libraries without imports.
Pro No operator precedence rules
(... within each of the 3 operator classes) makes reading code easier. Very simple parsing rules.
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.
Cons
Con Syntax is pure madness
quicksort=: (($:@(<#[), (=#[), $:@(>#[)) ({~ ?@#)) ^: (1<#)
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.