docs: clarify onMount with non-synchronous handlers (#5053)

4 years ago · dc73b735ce
parent 6e2b81663c
commit dc73b735ce
1 changed files with 2 additions and 0 deletions
--- a/site/content/docs/03-run-time.md
+++ b/site/content/docs/03-run-time.md
@ -50,6 +50,8 @@ If a function is returned from `onMount`, it will be called when the component i
 </script>
 ```

+> This behaviour will only work when the function passed to `onMount` *synchronously* returns a value. `async` functions always return a `Promise`, and as such cannot *synchronously* return a function.
+
 #### `beforeUpdate`

 ```js