### Author:  [@zerg000000](https://clojureverse.org/u/zerg000000)
#### Post date: [December 14, 2017, 4:46am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/21 "2017-12-14T04:46:52Z")
let try~
```auto
{
"dependencies": {
"left-pad": "1.2.0"
}
}
```
`npm install`
`lumo`
```auto
cljs.user=> (require '[left-pad :as lp])
nil
cljs.user=> (lp "foo" 5)
" foo"
```
seems nice!
---
### Author:  [@jiyinyiyong](https://clojureverse.org/u/jiyinyiyong)
#### Post date: [December 14, 2017, 6:29am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/22 "2017-12-14T06:29:46Z")
Good~
```clojure
=>> lumo
Lumo 1.7.0
ClojureScript 1.9.908
Node.js v8.4.0
Docs: (doc function-name-here)
(find-doc "part-of-name-here")
Source: (source function-name-here)
Exit: Control+D or :cljs/quit or exit
cljs.user=> (require '["md5" :as md5])
nil
cljs.user=> md5
#object[Function]
```
---
### Author:  [@plexus](https://clojureverse.org/u/plexus)
#### Post date: [December 14, 2017, 7:14am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/23 "2017-12-14T07:14:55Z")
Yup, that syntax is standard Clojurescript now, it should be supported no matter which tool you’re using.
---
### Author:  [@jiyinyiyong](https://clojureverse.org/u/jiyinyiyong)
#### Post date: [December 14, 2017, 8:51am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/24 "2017-12-14T08:51:08Z")
Where did that happen? Last time I saw it, it was still in debate?
---
### Author:  [@zerg000000](https://clojureverse.org/u/zerg000000)
#### Post date: [December 14, 2017, 8:55am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/25 "2017-12-14T08:55:35Z")
seems like 1.9.854
>
---
### Author:  [@plexus](https://clojureverse.org/u/plexus)
#### Post date: [December 14, 2017, 10:12am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/26 "2017-12-14T10:12:25Z")
Here’s the blog post that introduced that
[https://clojurescript.org/news/2017-07-12-clojurescript-is-not-an-island-integrating-node-modules](https://clojurescript.org/news/2017-07-12-clojurescript-is-not-an-island-integrating-node-modules)
---
### Author:  [@jwr](https://clojureverse.org/u/jwr)
#### Post date: [December 18, 2017, 12:57pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/27 "2017-12-18T12:57:27Z")
> [@plexus](#):
>
> It bothers me to celebrate this kind of negativity. It also bothers me that this talks about “Clojure being slow” when it’s really “Clojure startup time being slow”.
FWIW, I didn’t take this as negativity, but rather pointing out an issue (the elephant in the room). I think we should pay attention to this issue. I use Clojure for lots of things and while I’m very happy with server code performance, developing could definitely use speed improvements. `cider-jack-in` takes so long that I often go and get coffee, and if ClojureScript compilation were faster, I’d be much happier, too.
I understand there are good reasons for why it is slow, but this doesn’t mean we shouldn’t pretend it isn’t. Progress is being made and things are getting faster.
---
### Author:  [@bdesham](https://clojureverse.org/u/bdesham)
#### Post date: [December 18, 2017, 6:31pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/28 "2017-12-18T18:31:00Z")
The startup time is especially painful for me when I’m doing something like formatting code with cljfmt. I’m using [these Boot tasks](https://gist.github.com/bartojs/83a096ecb1221885ddd1) to integrate cljfmt with Boot and running `boot fmt` takes over 24 seconds to run on one one-line file. Am I “doing it wrong”? Should I be running this workflow from a REPL somehow instead?
---
### Author:  [@martinklepsch](https://clojureverse.org/u/martinklepsch)
#### Post date: [December 18, 2017, 8:16pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/29 "2017-12-18T20:16:44Z")
FWIW there’s a [nodejs version of `cljfmt`](https://github.com/snoe/node-cljfmt) on npm that starts up much faster. 🙂
---
### Author:  [@bdesham](https://clojureverse.org/u/bdesham)
#### Post date: [December 18, 2017, 9:57pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/30 "2017-12-18T21:57:05Z")
I came across that before but I guess I wrote it off because there had been an “update dependencies” PR open for six months. But thank you for the link 🙂
In general, though, is “find a ClojureScript version” the go-to advice for any kind of tooling where a 20-second startup time is unacceptable?
---
### Author:  [@jackrusher](https://clojureverse.org/u/jackrusher)
#### Post date: [December 19, 2017, 9:19am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/31 "2017-12-19T09:19:18Z")
I tend to do most things using a long-lived JVM process controlled from within `emacs`.
---
### Author:  [@martinklepsch](https://clojureverse.org/u/martinklepsch)
#### Post date: [December 19, 2017, 11:20am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/32 "2017-12-19T11:20:20Z")
> [@bdesham](#):
>
> In general, though, is “find a ClojureScript version” the go-to advice for any kind of tooling where a 20-second startup time is unacceptable?
I wish I had a better answer but yeah I think at this point in time that’s often the most feasible approach.
---
### Author:  [@shakdwipeea](https://clojureverse.org/u/shakdwipeea)
#### Post date: [December 20, 2017, 12:38pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/33 "2017-12-20T12:38:54Z")
Can you share some more details about this workflow ?
I’m a bit confused.
Is this the jvm started by the build tools eg. boot repl and reloading deps or controlling another jvm process?
---
### Author:  [@jackrusher](https://clojureverse.org/u/jackrusher)
#### Post date: [December 20, 2017, 4:29pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/34 "2017-12-20T16:29:48Z")
`lein repl` in a project, connect to it from `emacs` using `cider-connect`. One of things that makes this work well is having something like [alembic](https://github.com/pallet/alembic) in your main `lein` config so that you can pull in any deps you need without restarting.
---
### Author:  [@didibus](https://clojureverse.org/u/didibus)
#### Post date: [December 23, 2017, 8:37am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/35 "2017-12-23T08:37:54Z")
What I still ask myself is why ClojureScript doesn’t suffer from having to load, compile and init all namespaces in start-up?
If the culprit is Clojure and not the JVM, does ClojureScript bootstraps in a different way which solves exponentially the slow start-up times?
Or is it indirectly the JVM’s fault, in that load, compile and init are exponentially slower on the JVM then they are on V8?
One thought I had is, what if Clojure fns shared a class per namespace? Would this be doable? Would it speed up start-up and lower overall memory footprint?
---
### Author:  [@danielo515](https://clojureverse.org/u/danielo515)
#### Post date: [April 10, 2018, 6:37am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/36 "2018-04-10T06:37:51Z")
Just to be clear, is Clojure startup time allways high or just for big projects or during development? I mean, a compiled small program will take that long to startup too?
---
### Author:  [@jackrusher](https://clojureverse.org/u/jackrusher)
#### Post date: [April 10, 2018, 8:38am UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/37 "2018-04-10T08:38:39Z")
JVM Clojure programs typically take a long time to start, though by “a long time” we mean a few seconds. Compiled ClojureScript programs running in Node start much faster (~100ms).
---
### Author:  [@danielo515](https://clojureverse.org/u/danielo515)
#### Post date: [April 10, 2018, 12:20pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/38 "2018-04-10T12:20:34Z")
> [@jackrusher](#):
>
> Compiled ClojureScript programs running in Node start much faster (~100ms).
And that is the reason why I chose cljs for scripting, but I wanted to know how much does it take on clojure, because if it is one second vs 100ms I can live with it.
---
### Author:  [@dnolen](https://clojureverse.org/u/dnolen)
#### Post date: [April 10, 2018, 1:55pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/39 "2018-04-10T13:55:54Z")
> [@danielo515](#):
>
> And that is the reason why I chose cljs for scripting, but I wanted to know how much does it take on clojure, because if it is one second vs 100ms I can live with it.
Clojure doesn’t take longer than a second to start. If it takes longer than a second to run a simple script that almost always means you’re using some other thing that’s adding significant overhead - lein, boot, etc.
---
### Author:  [@didibus](https://clojureverse.org/u/didibus)
#### Post date: [April 10, 2018, 3:52pm UTC](https://clojureverse.org/t/tricks-to-make-clojure-startup-time-faster/1176/40 "2018-04-10T15:52:11Z")
Small scripts should start in around 1 second. There are cases where Clojure starts faster then ClojureScript. And if your script does a lot of CPU work, the speedup in execution time you get from Clojure can supersede the startup overhead, meaning the total execution time could still be faster in Clojure.
Take a look at this comparison: [https://github.com/kkinnear/zprint/blob/master/doc/filter.md#performance-results](https://github.com/kkinnear/zprint/blob/master/doc/filter.md#performance-results)
This is for a command line tool, and Clojure ends up being faster.
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