# Need help with writing macros for ClojureScript
**URL:** https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671
**Category:** Beginners
**Tags:** macros, clojurescript
**Created:** [October 11, 2020, 9:41pm UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671 "2020-10-11T21:41:43Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@u473t8](https://clojureverse.org/u/u473t8)
#### Post date: [October 11, 2020, 9:41pm UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/1 "2020-10-11T21:41:43Z")
For instance I have a macros in `my-macros` CLJ namespace (just a `let` macros copied from the clojure core) :
```auto
(ns my-macros)
(defmacro alt-let
[bindings & body]
(assert-args
(vector? bindings) "a vector for its binding"
(even? (count bindings)) "an even number of forms in binding vector")
`(let* ~(destructure bindings) ~@body))
```
I also have `my-macros` CLJS namespace that includes only:
```auto
(ns my-macros
(:require-macros [my-macros]))
```
This macros works fine when I use it in my clojurescript code this way:
```auto
(ns my-namespace
(:require [my-macros :refer-macros [alt-let]]))
(alt-let [[a b] [1 2]]
(js/console.log (+ a b)))
```
But if I try to do associative destructuring I get following errors:
```auto
(alt-let [{:keys [a b]} {:a 1 :b 2}]
(js/console.log (+ a b)))
```
```auto
No such namespace: clojure.lang.PersistentHashMap, could not locate clojure/lang/PersistentHashMap.cljs, clojure/lang/PersistentHashMap.cljc, or JavaScript source providing "clojure.lang.PersistentHashMap"
Use of undeclared Var clojure.lang.PersistentHashMap/create
```
Why do these errors occur and how to overcome this issue?
---
### Author:  [@jiyinyiyong](https://clojureverse.org/u/jiyinyiyong)
#### Post date: [October 12, 2020, 3:29am UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/2 "2020-10-12T03:29:01Z")
looks strange, where did the identifier `create` come from?
---
### Author:  [@thheller](https://clojureverse.org/u/thheller)
#### Post date: [October 12, 2020, 8:07am UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/3 "2020-10-12T08:07:18Z")
You are using the Clojure macro variants of `let*` and `destructure` since the macros run in Clojure and everything defaults to using `clojure.core`. Instead use the CLJS variant via `cljs.core/destructure` in the macro and everything should be fine.
---
### Author:  [@u473t8](https://clojureverse.org/u/u473t8)
#### Post date: [October 12, 2020, 8:53am UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/4 "2020-10-12T08:53:32Z")
I’ve tried rewriting CLJ namespace to CLJC like this:
```auto
(ns my-macros
(:require #?(:cljs [cljs.core :as cljs]))
#?(:cljs
(cljs/defmacro alt-let
[bindings & body]
(assert-args
(vector? bindings) "a vector for its binding"
(even? (count bindings)) "an even number of forms in binding vector")
`(cljs/let* ~(cljs/destructure bindings) ~@body))
:clj
(defmacro alt-let
[bindings & body]
(assert-args
(vector? bindings) "a vector for its binding"
(even? (count bindings)) "an even number of forms in binding vector")
`(let* ~(destructure bindings) ~@body))
```
but I still get the same errors.
---
### Author:  [@thheller](https://clojureverse.org/u/thheller)
#### Post date: [October 12, 2020, 10:42am UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/5 "2020-10-12T10:42:22Z")
This is not how macros work. Don’t use CLJC unless you really understand how macros work. I wrote a [post](https://code.thheller.com/blog/shadow-cljs/2019/10/12/clojurescript-macros.html) explaining macros step by step, maybe that helps.
This should be about all you need (in a `.clj`) file.
```auto
(ns my-macros)
(defmacro alt-let
[bindings & body]
(assert-args
(vector? bindings) "a vector for its binding"
(even? (count bindings)) "an even number of forms in binding vector")
`(let* ~(cljs.core/destructure bindings) ~@body))
```
---
### Author:  [@u473t8](https://clojureverse.org/u/u473t8)
#### Post date: [October 12, 2020, 12:05pm UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/6 "2020-10-12T12:05:40Z")
This doesn’t work too, I get the same errors. By the way, how is `cljs/core` namespace supposed to work if I want to use this macros in pure clojure? This is the reason I’ve tried to put this macros in a CLJC namespace.
---
### Author:  [@thheller](https://clojureverse.org/u/thheller)
#### Post date: [October 12, 2020, 1:04pm UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/7 "2020-10-12T13:04:29Z")
If you want to write the macro in CLJC then the macro must live in the `:clj` portion of the code and the macro must check whether it is supposed to emit CLJS code or CLJ code. Using a reader-conditional to put a macro in `:cljs` does not work.
```clojure
#?(:clj
(defmacro a-thing [& args]
(if (:ns &env) ;; this only exists when expanding CLJS code
`(cljs-code)
`(clj-code))))
```
---
### Author:  [@system](https://clojureverse.org/u/system)
#### Post date: [April 13, 2021, 1:04am UTC](https://clojureverse.org/t/need-help-with-writing-macros-for-clojurescript/6671/8 "2021-04-13T01:04:34Z")
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