Coming from a background of very little lisp and no clojure. If I'm not part of the target audience, then feel free to ignore these comments. Most of the tutorial was comprehensible and very instructive, however.

loop/recur not sure what's happening - is it a macro? b/c it doesn't look like a function call. What's the syntax mean?

defmulti the syntax is totally opaque to me.

protocols...are polymorphic functions? What's the difference between a protocol and a function? Or is that all it is? A bit more explanation would be much appreciated. For example, what's the significance of the word this in the following (defprotocol MyProtocol (awesome [this])). Changing it to "thing" or "cat" seems to have no effect.

Maybe if you showed the "ILookup" protocol definition or something it would make more sense.

Is there any difference between (extend-protocol protocol type ...) and (extend-type type protocol ...)?

Fantastic tutorial, on the whole!

I'm getting an error upon evaluating that very first namespace form:

"Invalid behavior: :lt.plugins.clojure/eval!"
TypeError: Cannot call method 'call' of undefined
    at notify (/opt/LightTable/plugins/clojure/clojure_compiled.js:1259:24)
    at check_all (/opt/LightTable/plugins/clojure/clojure_compiled.js:1274:83)
    at run_local_server (/opt/LightTable/plugins/clojure/clojure_compiled.js:1209:110)
    at try_connect (/opt/LightTable/plugins/clojure/clojure_compiled.js:347:45)
    at lt.objs.eval.find_client (file:///opt/LightTable/core/node_modules/lighttable/bootstrap.js:29877:16)
    at lt.objs.eval.get_client_BANG_ (file:///opt/LightTable/core/node_modules/lighttable/bootstrap.js:29907:32)
    at Function.__BEH__eval_BANG_ (/opt/LightTable/plugins/clojure/clojure_compiled.js:412:69)
    at c (file:///opt/LightTable/core/node_modules/lighttable/bootstrap.js:6196:14)
    at a (file:///opt/LightTable/core/node_modules/lighttable/bootstrap.js:6236:18)
    at lt.object.raise_STAR_ (file:///opt/LightTable/core/node_modules/lighttable/bootstrap.js:17890:74)

Is the error that I get. I am connected to LightTable UI, and have attempted to evaluate the first form.

I'm guessing this is a dumb error on my part, but since this is a tutorial for first-timers I figured I'd ask.

This snippet on exceptions is obscure. How, exactly, does :default work as a catch-all here, and does it have wider application? I know it is used in multi-methods, but have not found any other references to it.

;; JavaScript unfortunately allows you to throw anything. You can handle
;; this in ClojureScript with the following.

(try
  (throw (js/Error. "Oops"))
  (catch :default e
    e))

I have had to track down the following syntax once before, and I think it deserves more explanation.

;; We can use property access with `set!` to change the fill color of a
;; a canvas rendering context.

(set! (.-fillColor ctxt) "#ffffff")

I'm talking about the .-fillColor.

Starting from here, you show examples of extensions of native Javascript objects. But syntax is not clear :

(extend-type string ...)
(extend-type js/Date ...)
(extend-type number ...)

In Javascript, string and number are written String and Number. Why are they lowercase here whereas Date is accessed through js and with the normal Javascript case ?

https://github.com/swannodette/lt-cljs-tutorial/blob/master/lt-cljs-tutorial.cljs#L1335-L1355

These lines of code and comments seem to suggest that there is some sort of real difference between extend-type and extend-protocol:

;; Or you can extend a protocol on a defrecord.

I wasn't sure, so I read up on them in the docs. The docs for extend-protocol state:

Useful when you want to provide several implementations of the same
protocol all at once. [...] Expands into calls to extend-type

So am I right in assuming that extend-protocol is but a convenience macro that always expands to extend-type calls? If so, the marked lines seem a little bit odd, as we're getting nothing out of using extend-protocol instead of extend-type for a single defrecord, the syntax just seems flipped around and it left me thinking there was a fundamental difference between the two.

I tried running the lt-cljs-tutorial (freshly cloned) on a new Mac (OS X 10.13.1) and new d/l of LightTable 0.8.1.

After adding the connection as directed I tried evaluating the namespace form and got the output below. I have run all this before without a problem on another platform. Has something changed?

We couldn't connect.

Looks like there was an issue trying to connect to the project. Here's what we got:
final project: {:description A local light table project, :compile-path /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/target/classes, :deploy-repositories [[clojars {:url https://clojars.org/repo/, :password :gpg, :username :gpg}]], :group local-client, :resource-paths (/private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/dev-resources /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/resources), :uberjar-merge-with {META-INF/plexus/components.xml leiningen.uberjar/components-merger, data_readers.clj leiningen.uberjar/clj-map-merger, #"META-INF/services/." [clojure.core/slurp (fn [p1__949__951__auto__ p2__950__952__auto__] (clojure.core/str p1__949__951__auto__
p2__950__952__auto__)) clojure.core/spit]}, :name local-client, :checkout-deps-shares [:source-paths :test-paths :resource-paths :compile-path #'leiningen.core.classpath/checkout-deps-paths], :source-paths (/private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/src), :eval-in :subprocess, :repositories [[central {:url https://repo1.maven.org/maven2/, :snapshots false}] [clojars {:url https://clojars.org/repo/}]], :test-paths (/private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/test), :target-path /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/target, :prep-tasks [javac compile], :native-path /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/target/native, :offline? false, :root /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources, :pedantic? ranges, :clean-targets [:target-path], :plugins [], :plugin-repositories [[central {:url https://repo1.maven.org/maven2/, :snapshots false}] [clojars {:url https://clojars.org/repo/}]], :version 0.0.1, :jar-exclusions [#"^."], :global-vars {}, :uberjar-exclusions [#"(?i)^META-INF/[^/].(SF|RSA|DSA)$"], :jvm-opts [], :dependencies ([org.clojure/clojure 1.5.1] [org.clojure/tools.nrepl 0.2.10 :exclusions ([org.clojure/clojure])] [clojure-complete/clojure-complete 0.2.3 :exclusions ([org.clojure/clojure])] [lein-light-nrepl/lein-light-nrepl 0.1.3] [lein-light-nrepl-instarepl/lein-light-nrepl-instarepl 0.3.1]), :release-tasks [[vcs assert-committed] [change version leiningen.release/bump-version release] [vcs commit] [vcs tag] [deploy] [change version leiningen.release/bump-version] [vcs commit] [vcs push]], :repl-options {:nrepl-middleware [lighttable.nrepl.handler/lighttable-ops], :init (clojure.core/swap! lighttable.nrepl.core/my-settings clojure.core/merge {:name LightTable-REPL, :project (quote {:description A local light table project, :compile-path /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/target/classes, :deploy-repositories [[clojars {:url https://clojars.org/repo/, :password :gpg, :username :gpg}]], :group local-client, :resource-paths (/private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/dev-resources /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/resources), :uberjar-merge-with {META-INF/plexus/components.xml leiningen.uberjar/components-merger, data_readers.clj leiningen.uberjar/clj-map-merger, #"META-INF/services/." [clojure.core/slurp (fn* [p1__949__951__auto__ p2__950__952__auto__] (clojure.core/str p1__949__951__auto__
p2__950__952__auto__)) clojure.core/spit]}, :name local-client, :checkout-deps-shares [:source-paths :test-paths :resource-paths :compile-path #'leiningen.core.classpath/checkout-deps-paths], :source-paths (/private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/src), :eval-in :subprocess, :repositories [[central {:url https://repo1.maven.org/maven2/, :snapshots false}] [clojars {:url https://clojars.org/repo/}]], :test-paths (/private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/test), :target-path /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/target, :prep-tasks [javac compile], :native-path /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/target/native, :offline? false, :root /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources, :pedantic? ranges, :clean-targets [:target-path], :plugins [], :plugin-repositories [[central {:url https://repo1.maven.org/maven2/, :snapshots false}] [clojars {:url https://clojars.org/repo/}]], :version 0.0.1, :jar-exclusions [#"^."], :global-vars {}, :uberjar-exclusions [#"(?i)^META-INF/[^/]*.(SF|RSA|DSA)$"], :jvm-opts [], :dependencies ([org.clojure/clojure 1.5.1] [org.clojure/tools.nrepl 0.2.10 :exclusions ([org.clojure/clojure])] [clojure-complete/clojure-complete 0.2.3 :exclusions ([org.clojure/clojure])]), :release-tasks [[vcs assert-committed] [change version leiningen.release/bump-version release] [vcs commit] [vcs tag] [deploy] [change version leiningen.release/bump-version] [vcs commit] [vcs push]], :test-selectors {:default (constantly true)}})})}, :test-selectors {:default (constantly true)}}
java.io.IOException: Permission denied. Please check your access rights for /private/var/folders/p7/glb8sl9d6vz8y10f0vw493n00000gn/T/AppTranslocation/76839D72-2CAE-4778-BEA4-995C1631A8B8/d/LightTable.app/Contents/Resources/app/plugins/Clojure/runner/resources/.nrepl-port
at leiningen.repl$repl.doInvoke(repl.clj:317)
at clojure.lang.RestFn.invoke(RestFn.java:425)
at leiningen.light_nrepl$light.invoke(light_nrepl.clj:77)
at leiningen.light_nrepl$_main.doInvoke(light_nrepl.clj:85)
at clojure.lang.RestFn.applyTo(RestFn.java:137)
at leiningen.light_nrepl.main(Unknown Source)

I receive the following error when trying to evaluate line 81 (https://github.com/swannodette/lt-cljs-tutorial/blob/master/lt-cljs-tutorial.cljs#L81). Should I not be evaluating there or is this another issue?

ReferenceError: lt_cljs_tutorial is not defined
    at eval (/Users/bliss/Code/lt-cljs-tutorial/lt-cljs-tutorial.cljs[eval7]:81:1)
    at eval (native)
    at Function.eval (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:33785:461)
    at b (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:6188:14)
    at a (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:6234:18)
    at cljs.core.do_dispatch (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:13583:26)
    at cljs.core.MultiFn.cljs$core$IMultiFn$_dispatch$arity$2 (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:13655:32)
    at cljs.core._dispatch (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:13568:14)
    at a (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:13662:32)
    at b [as call] (file:///Applications/LightTable/LightTable.app/Contents/Resources/app.nw/core/node_modules/lighttable/bootstrap.js:13666:14)

When I reach this line:

(def x 1)

And I hit Control-Enter:

ReferenceError: lt_cljs_tutorial is not defined
    at eval (/home/al/lt-cljs-tutorial.cljs[eval48]:77:1)
    at eval (native)
    at Function.eval (app://lighttable/core/node_modules/lighttable/bootstrap.js:33600:461)
    at b (app://lighttable/core/node_modules/lighttable/bootstrap.js:6143:14)
    at a (app://lighttable/core/node_modules/lighttable/bootstrap.js:6189:18)
    at cljs.core.do_dispatch (app://lighttable/core/node_modules/lighttable/bootstrap.js:13499:26)
    at cljs.core.MultiFn.cljs$core$IMultiFn$_dispatch$arity$2 (app://lighttable/core/node_modules/lighttable/bootstrap.js:13571:32)
    at cljs.core._dispatch (app://lighttable/core/node_modules/lighttable/bootstrap.js:13484:14)
    at a (app://lighttable/core/node_modules/lighttable/bootstrap.js:13578:32)
    at b [as call] (app://lighttable/core/node_modules/lighttable/bootstrap.js:13582:14)

I'm new to both LightTable and ClojureScript so I might be missing something but the tutorial worked fine until that point.

Hi David, shouldn't we add regex as well, even if js regex are not fully supported?

https://github.com/swannodette/lt-cljs-tutorial/blob/master/lt-cljs-tutorial.cljs#L490-L493

Maybe add something which evaluates to true for identical? here eg.

(def my-vec [1 2 3])
(def your-vec [1 2 3])
(def also-my-vec my-vec)

(identical? my-vec your-vec)

(identical? my-vec also-my-vec)

I had trouble running some of the examples in older versions of Light Table.

For example, evaluating

(def another-array #js [1 2 3])

I would get the error

No reader function for tag js core.clj:4327 clojure.core/ex-info

This seems to have been fixed a while ago in Light Table, but I thought I would let you know if others run into this issue. Maybe we could update the README with versions that work correctly.

I saw this today which looks wrong.

Specifically, this part:

Am I missing something or is this a bug?

I'm following the tutorial first step, but with leiningen installed and light table 0.8.0-alpha I've got the error message : no file or url found for cljs connection when I hit cmd-enter just after the namespace command