From d4e150adc98cb59cf8595cd01b3e78ee22bc2b1f Mon Sep 17 00:00:00 2001
From: "Luke \"Jared\" Bennett" <lbennett@gitlab.com>
Date: Tue, 16 May 2017 16:39:13 +0000
Subject: Update design_patterns.md to include maintainer decision on custom
 errors

---
 doc/development/fe_guide/design_patterns.md | 40 +++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/doc/development/fe_guide/design_patterns.md b/doc/development/fe_guide/design_patterns.md
index e05887a19af..1555c2b1cc7 100644
--- a/doc/development/fe_guide/design_patterns.md
+++ b/doc/development/fe_guide/design_patterns.md
@@ -76,3 +76,43 @@ You can find an example of the above in this [class][container-class-example];
 
 
 [container-class-example]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/mini_pipeline_graph_dropdown.js
+
+## Custom errors
+
+Custom/namespaced error are not accepted. You should just use a string.
+
+Example:
+
+### bad
+```js
+class NamespacedError extends Error {
+    ... custom Error logics ...
+}
+
+const NamespacedObj = {
+    someMethod() {
+        throw NamespacedError;
+    }
+};
+
+try {
+    NamespacedObj.someMethod()
+} catch (error) {
+    if (error instanceof NamespaceError)  ...
+}
+```
+
+### good
+```js
+const NamespacedObj = {
+    someMethod() {
+        throw 'some string';
+    }
+};
+
+try {
+    NamespacedObj.someMethod()
+} catch (error) {
+    if (error === 'some string')  ...
+}
+```
\ No newline at end of file
-- 
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