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hoplon
javelin
Clojure2013–2026
hoplon / javelin

javelin

Spreadsheet-like dataflow programming in ClojureScript.

11Distinct people
14Mentions
0Explicit recommenders
826GitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

Spreadsheet-like dataflow programming in ClojureScript.

GitHub

Where it is used

No documented product use was verified in the last source check.

What people are saying

No recommendation phrase was found in the indexed comments.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 5:04:57 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year14 dated mentions

Observed mentions: 2013-02-15 22:47:32 UTC to 2026-07-21 05:38:46 UTC.

012342013-01-01 00:00:00 UTC to 2014-01-01 00:00:00 UTC (exclusive): 3 mentions; 1 submissions, 2 comments20132014-01-01 00:00:00 UTC to 2015-01-01 00:00:00 UTC (exclusive): 3 mentions; 0 submissions, 3 comments2015-01-01 00:00:00 UTC to 2016-01-01 00:00:00 UTC (exclusive): 4 mentions; 0 submissions, 4 comments2016-01-01 00:00:00 UTC to 2017-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2017-01-01 00:00:00 UTC to 2018-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2018-01-01 00:00:00 UTC to 2019-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments20192020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2026-01-01 00:00:00 UTC to 2027-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments. Incomplete calendar period.2026*

* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20132013-01-01 00:00:00 UTC2014-01-01 00:00:00 UTC312
20142014-01-01 00:00:00 UTC2015-01-01 00:00:00 UTC303
20152015-01-01 00:00:00 UTC2016-01-01 00:00:00 UTC404
20162016-01-01 00:00:00 UTC2017-01-01 00:00:00 UTC000
20172017-01-01 00:00:00 UTC2018-01-01 00:00:00 UTC000
20182018-01-01 00:00:00 UTC2019-01-01 00:00:00 UTC000
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC101
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC101
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC000
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC000
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC101
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC000
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC000
2026 (partial)2026-01-01 00:00:00 UTC2027-01-01 00:00:00 UTC101

What Hacker News says

14 sources
There are some languages that do this, especially reactive languages and there are some libraries for other languages that work kinda like this, for example Rx[1] works kinda like this or maybe Clojure's Javelin[2]. You could make an Rx-like system that works somewhat like that in C++, or you could use coroutines or a task-based system like Intel TBB to implement something kinda like this. It of course wouldn't be a first-class thing like in Concurnas, but I reckon you could implement the basic idea. As far as languages go, the ideas you showed look similar to how Esterel[3] works, or perhaps Occam[4]. [1] http://reactivex.io/ [2] https://github.com/hoplon/javelin [3] https://en.wikipedia.org/wiki/Esterel [4] https://en.wikipedia.org/wiki/Occam_(programming_language)
In The Concurnas Programming Language
> Glitches as demonstrated via the diamond pattern can be avoided by traversing the graph in topological order. This is correct for DAGs which only propagate value (as in Javelin[1] and my own library DerivableJS[2]), but for graphs which propagate events (as in Rx), topological sorting would only work for those parts of the graph which are effectively propagating value. Events don't have an inherent dedupe operation, so it is very difficult to even imagine ways in which glitch avoidance could be automatically enforced. It would certainly require semantic program analysis. Personally I think we should be avoiding the proliferation of events (as encouraged by Rx enthusiasts) for exactly this reason. Their imperative nature makes them very difficult to reason about. [1]: https://github.com/hoplon/javelin [2]: https://github.com/ds300/deriva
Read the rest
In Rx glitches aren't actually a problem
They aren't a problem if the operations at the leaves of the graph are idempotent, which is usually the case if these operations are UI repaints. If the operations are for other effects - such as Ajax calls - then glitch elimination is handy. Eliminating glitches at the dataflow level prevents debounce logic from leaking out to the code performing the effects, preserving the clarity and generality of that code. I find glitch elimination most useful when the dataflow graph is value-propagated, vs. event-propagated, as it is in the dataflow library I helped implement, Javelin - https://github.com/hoplon/javelin/ Javelin also supports transactional input, another feature that's helpful when building dataflow graphs on which effects other than UI-repaint are hung.
In Rx glitches aren't actually a problem
* figwheel -> https://github.com/adzerk-oss/boot-reload It's not as smart as figwheel because u can lose state, but it's mostly enough. We are actually quite fine with reloading the page manually most of the time. * uberjar: If you use http://boot-clj.com/ instead of lein, you won't have issues with left-over files, because boot allows every build step to create a unique temp dir which gets erased on next run. Content amongst these temp dirs can be shared by a git-like object store and build tasks pass a virtual immutable file-system (called a fileset) between each other. * templating: http://hoplon.io/ Your page is not a big data structure. It's an actual Clojure program, which generates DOM Elements directly. You can even call DOM Elements as functions to alter their attributes or their DOM children. Combined with https://github.com
Read the rest
/hoplon/javelin you get reactivity in an unobtrusive way. You can separate you app state with it, just like you put data into a spreadsheet and wire up a chart to it which will update automatically. Your DOM is the equivalent of that chart in this case. * cljs repl -> https://github.com/adzerk-oss/boot-cljs-repl but in practice it was hardly ever used by boot/hoplon people, so it's a bit neglected now. * server-client state sharing: Hoplon + Javelin + https://github.com/hoplon/castra It's a bit under-documented... probably because it's so super simple... :) Castra does a remote function call via XHR and puts the result into a Javelin cell. If that cell is wired up to a DOM element (attribute or content), either directly or transformed by a formula cell, then your DOM updates automatically once the XHR call finishes. Errors are placed into an error cell, which can also be wired to the DOM... * Falcor / GraphQL ... I have NOT done this yet but I'm planning to "just" pass Datomic queries via Castra to the backend and that's it. I can't "subscribe to live query" this way, but that's good enough for us. It's also just 1 HTTP end-point. No more RESTful rigidity... ;) * Vim/REPL: We are just fine with the good old `(print)` and `(serve {:reload true})` from https://github.com/pandeiro/boot-http on the backend. Also we just use Sublime Text with paredit and lispindent. It's super fast even on 4-5 year old machines... * Chestnut template / plugin: With boot this problem set shrinks to a size where distinction between template and plugin vanishes. You can create a .jar which defines a boot task. That task either creates a template project or defines a build step which u can intermix with other build steps using plain-vanilla function composition. Your environments are also just tasks combining specific build steps with specific options. Nothing custom or magical. * Om: Again: Try Hoplon. Fraction of the complexity. * CLJSJS: Your worries regarding extern files and maintenance are not a problem in practice really. We are maintaining a Semantic UI package https://github.com/exicon/hoplon-semantic-ui and just the other day I whipped up externs files for Google Analytics (3 lines), HubSpot (5 lines), Inspectlet (6 lines). See https://github.com/exicon/homepage/tree/master/src Disclaimer: I've started using Clojure ~10month ago. Never really used Lein but experienced all of its pains via Grunt and Gulp I suspect... Trained ~8 people to work with Boot & Hoplon during these months by pair programming with them. We don't really miss anything else, though we looked into Emacs, Vim, IntelliJ, LightTable. There are some rough edges and missing documentation, but http://hoplon.discoursehosting.net/ and the #hoplon & #boot channels on http://clojurians.net/ Slack and freenode IRC https://botbot.me/freenode/hoplon/ were more than sufficient.
In ClojureScript Blues
I haven't watched that part of the video yet, but I've always believed that Rich's biggest blind-spot seems to be about not realizing how Clojure's macro system can be used to rewrite regular code into FRP. Just have a look at what a macro like Javelin [1] already enables [2] and imagine how powerful that would be when combined with 'live' Datolog queries where the query results in the browser will stay up to date with the results from the logic datalog query on Datomic. I've tried explaining it to Rich at EuroClojure 2012 but I'm pretty sure he was still thinking in terms of 'classic FRP' back then. [1] https://github.com/tailrecursion/javelin [2] http://www.infoq.com/presentations/ClojureScript-Javelin
In The Language-Language Matrix

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