From 4789af71fe107e137524bc7746b902e644aca2dc Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Tue, 3 Sep 2024 00:10:01 +0800
Subject: [PATCH] fixes #24031; js codegen bug for case statement with just
 else branch (#24047)

fixes #24031
---
 compiler/jsgen.nim              | 9 +++++++--
 tests/casestmt/tcase_issues.nim | 7 +++++++
 2 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 tests/casestmt/tcase_issues.nim

diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index d6310d5847f4b..e3c0b1f463261 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -1098,14 +1098,19 @@ proc genCaseJS(p: PProc, n: PNode, r: var TCompRes) =
           lineF(p, "break;$n", [])
     of nkElse:
       if transferRange:
-         lineF(p, "else{$n", [])
+        if n.len == 2: # a dangling else for a case statement
+          transferRange = false
+          lineF(p, "switch ($1) {$n", [cond.rdLoc])
+          lineF(p, "default: $n", [])
+        else:
+          lineF(p, "else{$n", [])
       else:
         lineF(p, "default: $n", [])
       p.nested:
         gen(p, it[0], stmt)
         moveInto(p, stmt, r)
         if transferRange:
-           lineF(p, "}$n", [])
+          lineF(p, "}$n", [])
         else:
           lineF(p, "break;$n", [])
     else: internalError(p.config, it.info, "jsgen.genCaseStmt")
diff --git a/tests/casestmt/tcase_issues.nim b/tests/casestmt/tcase_issues.nim
new file mode 100644
index 0000000000000..20a79df2c577f
--- /dev/null
+++ b/tests/casestmt/tcase_issues.nim
@@ -0,0 +1,7 @@
+discard """
+  targets: "c js"
+"""
+
+block: # bug #24031
+  case 0
+  else: discard
\ No newline at end of file