From 4c06a56e52184796280d9c19975f5317f3050cc9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Donny/=EA=B0=95=EB=8F=99=EC=9C=A4?= <kdy1997.dev@gmail.com>
Date: Sat, 15 Apr 2023 23:50:52 +0900
Subject: [PATCH] fix(es/minifier): Use UTF16 length for `str.length` (#7275)

**Related issue:**

 - Closes #7274.
---
 crates/swc_ecma_minifier/tests/exec.rs        | 19 +++++++++++++++++++
 .../src/simplify/expr/mod.rs                  |  2 +-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/crates/swc_ecma_minifier/tests/exec.rs b/crates/swc_ecma_minifier/tests/exec.rs
index 20b8fe3a8e1..6acfb06d7ac 100644
--- a/crates/swc_ecma_minifier/tests/exec.rs
+++ b/crates/swc_ecma_minifier/tests/exec.rs
@@ -10931,3 +10931,22 @@ fn issue_6914_3() {
         false,
     );
 }
+
+#[test]
+fn issue_7274() {
+    run_default_exec_test(
+        r###"
+        if (
+            // incorrect:
+            "😋📋👌".length === 3
+    
+            // correct:
+            // "😋📋👌".length === 6
+        ) {
+            // side effect
+            new Response(123);
+        }
+        console.log('PASS');
+        "###,
+    );
+}
diff --git a/crates/swc_ecma_transforms_optimization/src/simplify/expr/mod.rs b/crates/swc_ecma_transforms_optimization/src/simplify/expr/mod.rs
index 509bfadb4f8..701a194843c 100644
--- a/crates/swc_ecma_transforms_optimization/src/simplify/expr/mod.rs
+++ b/crates/swc_ecma_transforms_optimization/src/simplify/expr/mod.rs
@@ -154,7 +154,7 @@ impl SimplifyExpr {
                     self.changed = true;
 
                     *expr = Expr::Lit(Lit::Num(Number {
-                        value: value.chars().count() as f64,
+                        value: value.chars().map(|c| c.len_utf16()).sum::<usize>() as _,
                         span: *span,
                         raw: None,
                     }));