docs: explain mergeConfig skips null/undefined (#22325)

imxv · sunmozong · bluwy · web-flow · commit 2151f701dc98 · 2026-04-28T10:26:39.000+08:00
Co-authored-by: sunmozong &lt;sunmozong@kuaishou.com&gt;
Co-authored-by: Bjorn Lu &lt;bjornlu.dev@gmail.com&gt;
diff --git a/docs/guide/api-javascript.md b/docs/guide/api-javascript.md
@@ -312,6 +312,8 @@ function mergeConfig(
 
 Deeply merge two Vite configs. `isRoot` represents the level within the Vite config which is being merged. For example, set `false` if you're merging two `build` options.
 
+Note that `null` and `undefined` values in `overrides` are skipped and not merged. If you need to explicitly clear a value from `defaults`, modify the result of `mergeConfig` directly.
+
 ::: tip NOTE
 `mergeConfig` accepts only config in object form. If you have a config in callback form, you should call it before passing into `mergeConfig`.
 
