Suppose I have a javascript function as a string in cljs. Such as: (def s (str inc)) (= s "function cljs$core$inc(x){\nreturn (x + (1));\n}") how could I then call s, as in: (s 1) => 2

@john (js* "alert('my special JS code')") from: http://www.spacjer.com/blog/2014/09/12/clojurescript-javascript-interop/

@danvingo Thanks!

np!

Hi everybody. I’ve been using Clojure on the backend for some time now, and I would like to start with cljs, too. I have a toy web project in mind (Scrum Poker Web App), where users can simultainously pick cards, and the selection is pushed to other webclients immediately. Right now I need to pick frameworks, and found this page: https://github.com/hantuzun/awesome-clojurescript#web-framework—template. What would be a popular, but already well established choice for a front- and backend combination? My frontend experience is mainly restricted to Angular JS and the bloaty Java server side frameworks (I am not a fan of server side html generation…).

(I don’t have any experience with reactive programming, but also would like to have a shot at it)

@javahippie you could go with something like chord: https://github.com/jarohen/chord

and then choose any clj backend or cljs frontend you like

But if all you are doing is mostly broadcasting state changes between clients, you don't need too much on the backend

@javahippie on the frontend there's been a lot of interest in re-frame and Reagent

Does anyone know if it is possible to get the source of a function using cljs.repl/source programmatically, while not at the repl?

chord looks great, and I will check re-frame and reagent. Thank you very much, I appreciate your recommendations!

I'm guessing after advanced compilation, cljs.repl/source will no longer have access to the original symbols?

@javahippie absolutely!

hi guys, I would like to use this package https://github.com/algolia/instantsearch.js/tree/v2/packages/react-instantsearch in my application. What is the easiest way to do it ? Thanks

@john why do you need the source of a function? that will only lead to very questionable results at best

@thheller in order to serialize functions to be evaled in a webworker

don't do that 🙂

why not? 🙂

can you guarantee that the function doesn't call other functions?

their source won't be in there

but why would you? just load the code in the webworker and send data over?

also it doesn't work with :advanced optimizations at all

since closure can't tell if you use things via eval

it's moreso of an experiment. I'd like to make a defworker which does a defn (with-meta name {:source (actual source)}).

then you can pass that function to a worker like you would to an agent. And the worker then updates its state, like a worker.

like an *agent, rather

Any defworkers you evaluate on an agent could potentially remember the function definitions on the worker side, allowing you to feed in a series of definitions to initialize it for something in particular

that doesn't work

But you wouldn't need the defworker if you could always get the source

the worker will always need more than just the source of one function

ie. cljs.core to have access to the collections CLJS offers

but webworkers makes this really easy

you can do importScripts in the worker

@thheller got all that. I've got a full replum repl running in the webworker with libraries loaded.

with butler shuttling data between them

then why send the function over if its already over there?

Why send a function to an agent?

I guess if you've already defined all your functions, you can just call a look up table on the worker side

but sometimes you're probably sending in functions created dynamically

I don't know what you are trying to do but serializing functions is bad in JS

pretty much bad in every language probably

Yea I'm noticing it's not easy, and maybe a bad idea 🙂

definitely bad idea yes 😉

I tried doing something similar a few years back in clojure

agents in clojurescript is too cool to resist though, so it's a fun experiment 🙂

horrible idea in the end 🙂

they are not agents though

Well, they don't participate with an stm

They don't share data and scope in the same way agents do

but clojure agents are meant to be asynchronous anyway, so it's somewhat similar

I prefer to think in terms of core.async

you send things on one channel and get things back on another

Yea, but a webworker is a potentially real system thread

technically its more like a new process

threads share memory, webworkers dont

right, so you have to marshal code. It's not pretty

so everything back and forth has to be serialized

in many instances that is more expensive than just not using a worker in the first place

well depends on the calculations you are doing I guess

round robin on a pool of hot webworkers couldn't hurt, depending on the load 🙂

doesn't change a thing

the main thread still has to read the data the workers produce

but yeah it all depends on the cost of the calculation

you can still easily starve the main thread if its reading too much data

well, if your calculation blocks longer than 40 milliseconds, why not send it off?

how much data does it require to send and receive?

assume you are using transit, how long do the write/read take?

the more data the worker needs the longer that takes

Yeah, it'll be interesting to see what the performance characteristics will be

Hi, I am trying to do a simple function check using spec in ClojureScript (:require [cljs.spec :as s] [cljs.spec.test :as test]... (defn my-index-of "Returns the index at which search appears in source" [source search] (clojure.string/index-of source search)) (s/fdef my-index-of :args (s/cat :source string? :search string?) :ret nat-int? :fn #(<= (:ret %) (-> % :args :source count))) and (test/check 'my-index-of) instead of returning a problem , always returns [] meaning basically that it doesn't do anything?

I am basically trying this in ClojureScript https://www.youtube.com/watch?v=W6crrbF7s2s

Hi, I also have a spec question, is there any way to add a humain friendly message to a spec when failing ?

@baptiste-from-paris https://clojurians.slack.com/archives/C1B1BB2Q3/p1489948793180526

i have a problem deploying. everything runs fine in figwheel but the release build throws an Error: [object Object] is not ISeqable...

:dependencies [[org.clojure/clojure "1.8.0" :scope "provided"]
                 [org.clojure/clojurescript "1.9.229" :scope "provided"]
                 [reagent "0.6.0"]
                 [org.clojure/data.xml "0.2.0-alpha2"]]

my lein build profile:

{:source-paths ["src" "env/prod/cljs"]
                        :compiler
                        {:output-to "public/js/app.js"
                         :output-dir "public/js/release"
                         :asset-path   "js/out"
                         :source-map false
                         :optimizations :advanced
                         :pretty-print false}}}}

Is there any reason not to have clj/cljs/cljc files containing the same namespace? For example lib.clj + lib+cljc + lib.cljs

not a good idea

since it’s possibly ambiguous (to someone looking at the codebase) which file you want lib.cljs to load for macros - I think .clj gets precedence?

it’s more common to just lib.cljc + lib.cljs

another optinon is just lib.cljc + self require for macros

@timrichardt Looks like you're trying to perform a sequence operation on a javascript object.

@janetacarr indeed, the whole thing is related to the externs stuff. i have to spend some time reading how the compiler works... 🙂

with :optimizations :simple it works

I’ve run this code through an extern generator, but it doesn’t generate one for a function named clearAll in the React Virtualized library Generator: http://jmmk.github.io/javascript-externs-generator/ Loaded JavaScripts: * https://cdnjs.cloudflare.com/ajax/libs/react/15.4.2/react-with-addons.js * https://cdnjs.cloudflare.com/ajax/libs/react-virtualized/9.0.3/react-virtualized.js

Why

(cc @juhoteperi)

@borkdude I think react-virtualized does some dynamic magic to add those methods the the class

You can search for clearAll in the JS file to find some suspicious code where methods are defined as array of JS objects

@juhoteperi What’s the recommended way for cljsjs to add something manually to a generated extern file?

@borkdude Just manually edit the code and add a comment to the top of the file that it has been modified manually

return (0, _createClass3.default)(CellMeasurerCache, [ {
                    key: "clear",
                    value: function(rowIndex, columnIndex) {
                        var key = this._keyMapper(rowIndex, columnIndex);
                        delete this._cellHeightCache[key], delete this._cellWidthCache[key];
                    }
                }, {
                    key: "clearAll",
                    value: function() {
                        this._cellHeightCache = {}, this._cellWidthCache = {};
                    }

TypeScript has type definitions for react-virtualized (and hundreds of other libraries): https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/react-virtualized/index.d.ts

It is on my todo list to write tool to convert typescript definitions to Closure externs

@juhoteperi I think this is a ES6 construct? https://github.com/bvaughn/react-virtualized/blob/ed887bb8e7141ac04081d50fa6b1f22fde429bf3/source/CellMeasurer/CellMeasurerCache.js#L129

@borkdude it’s just a normal class

CellMeasurerCache.prototype.clearAll = function () {}

@anmonteiro Problem is that in webpack output it is not, so extern generator doesn't find it

yeah, I’m saying for the extern stuff

yeah

sorry, meant for writing the manual extern

should work if you write that, right?

yes

there you go, that’s all I’m saying

wow, ((gobject/get “clear”) 0 0) instead of (.clear cache 0 0) doesn’t even work because of this being the wrong value?

Uncaught TypeError: this._keyMapper is not a function

@borkdude right, in such case (.call f this p1 p2 …)

this expected, you would run into the same issue in javascript as well

(.call (gobject/get cache "clear") cache 0 0)

ok

Thanks 🙂

btw. cljs-oops does “this retargeting” for you: https://github.com/binaryage/cljs-oops/releases/tag/v0.5.0

it would be (ocall cache “clear” 0 0)

nice

I’ll use that immediately

What’s the deal again with refer-macros, isn’t that needed anymore?

I see here that the author doesn’t use it: https://github.com/binaryage/cljs-oops#integrate-with-your-project

http://dev.clojure.org/jira/browse/CLJS-1507

@borkdude it’s not needed because the .cljs namespace self-requires them https://github.com/binaryage/cljs-oops/blob/master/src/lib/oops/core.cljs#L14

so the CLJS compiler can infer them automatically

magic here: https://github.com/binaryage/cljs-oops/blob/master/src/lib/oops/core.cljs#L14

aah

I just recently discovered that this can be used to avoid writing reader conditionals when requiring macros from cljc files - for code targeting both clojure and clojurescript: https://github.com/binaryage/env-config/blob/master/src/lib/env_config/impl/macros.cljs

and inside macro, I can decide what kind of code I want to generate, depending on current environment: https://github.com/binaryage/env-config/blob/master/src/lib/env_config/impl/macros.clj#L20

usage here: https://github.com/binaryage/env-config/blob/master/src/lib/env_config/impl/coercers.cljc#L4

...hate to sprinkle reader conditionals all over my code

I need help trying to make a clj project compatible with cljs

I renamed the main file from core.clj to core.cljc

but when I do lein compile it does not generate any classes

abarylko what is your :aot setting in project.clj?

if it’s not present, compile won’t output anything

you could try lein compile :all

I have :aot :all

D’oh, the answer was right below that code fragment

@noisesmith won't @abarylko want to switch to cljsbuild?

oh cljc

@john Do I need cljsbuid in order to compile cljc ?

@abarylko I'm guessing not. But if my memory serves, cljsbuild will compile cljc files as well.

most cljs consumers of your library will be using cljsbuild though. So it couldn't hurt to test with it.

hello guys, is there a way to resolve a symbol in cljsand then apply the function with the Var ?

Thanks @john & @noisesmith I'll try it out ....

or perhaps if you know of a project that uses cljc that I could take a look ...

@baptiste-from-paris only from a macro

yep, I just saw that

thx @anmonteiro

what is the preferred library to integrate react and cljs, these days?

@mikepence reagent, re-frame, quiescent, om

it isn’t clear to me if there is a “preferred"

thanks

I probably would suck at summarizing, but: * reagent = thin wrapper over react that just makes it more "cljs idiomatic” to use (not so OO). slightly “opinionated” (I guess) in its usage of RAtom (cljs atom wrapper) * re-frame = larger “framework” that uses reagent but also pulls together more libs to do things like routing, etc * quiesent = sort of like reagent with a few different goals in mind (good readme there), tries to be very “un-opionated" * om = another wrapper over react, more “opinionated" than others perhaps and was started(?) by David Nolen (lead cljs contributor)

I’m sure others could correct me on a bunch of that. However, all these projects seem to have pretty good docs.

after trying to create a macro that updates the meta data of a function, based on examples here: https://cljs.github.io/api/cljs.core/defn- and here: https://stackoverflow.com/questions/9177709/constant-definition-in-clojure

The results always have no metadata

it's like the meta data is getting stripped after the macro compiles

Anyone have an idea why they won't hold their meta data?

when testing from the repl

@john an example of your macro would be helpful

I’ve done that before and it worked

also, do you want the metadata on the function or on the var?

@anmonteiro just going with the defn- example:

(defmacro defn- [name & decls] (list* `defn (with-meta name (assoc (meta name) :private true)) decls))

If I put that in my macros.cljc file, it will run from the repl, the result has no attached metadata

so you should be seeing your metadata on the var

(my-def my-name …)

(meta #‘my-name)

@anmonteiro I'm not sure if I'd be better off working with the metadata of the fn or the var.

@anmonteiro that was it!

#'

I was forgetting to extract the var

Vars are static, so you’ll need to always have the name of the function at hand (i.e. can't get a function via a param and expect it to have metadata)

if you put the metadata on the function, you can call meta on the actual function value, which means the above use case will work

on the other hand, it’s not a JS function anymore, but a JS instance that implements IFn

tradeoffs...

hmm

in the above example, is it adding metadata to the fn or the var?

the var

Would something like this be attaching it to the fn?

(defmacro defn- [name & decls (with-meta (list* `defn name decls) (assoc (meta name) :private true))])

yes

kinda

🙂

well, parinfer clobbered my binding form 🙂

you’ll probably want (def symbol (with-meta (fn …)))

defn may return the function, or the var, depending if you’re in the REPL or not

Okay, so I'm getting close. But for some reason the metadata is dropping key-vals selectively:

(defmacro defn-with-source [name bindings & forms] `(def ~name (with-meta `(fn bindings [email protected]) (assoc (meta name) :const true :source true))))

(m/defn-with-source o [& a] (apply + a))

=> (meta o) {:const true}

:source true is not showing up

@john what are you going to build? some kind of dev tool? wonder why do you need fn sources, just curious

@darwin I'm experimenting with building agents, similar to clj agents, on top of webworks. So I have to shuttle code over to the worker agents.

and in the example above, I think ~(with-meta ... part is wrong

you want to emit with-meta I guess

I send the straight javascript to the worker, but I couldn't figure out how to easily apply the then compiled js to potentially cljs parameters, on the worker side