Fixes #5461 (#5467)

* Fixes #5461

* Update runtime-transpiler.test.ts

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

2 files changed, 29 insertions, 4 deletions

diff --git a/src/js_printer.zig b/src/js_printer.zig
index 57ef580b6..709672f29 100644
--- a/src/js_printer.zig
+++ b/src/js_printer.zig
@@ -3180,10 +3180,26 @@ fn NewPrinter(
                                         hex_chars[cursor.c & 15],
                                     });
                                 },
-                                else => {
-                                    p.print("\\u{");
-                                    std.fmt.formatInt(cursor.c, 16, .lower, .{}, p) catch unreachable;
-                                    p.print("}");
+
+                                else => |c| {
+                                    const k = c - 0x10000;
+                                    const lo = @as(usize, @intCast(first_high_surrogate + ((k >> 10) & 0x3FF)));
+                                    const hi = @as(usize, @intCast(first_low_surrogate + (k & 0x3FF)));
+
+                                    p.print(&[_]u8{
+                                        '\\',
+                                        'u',
+                                        hex_chars[lo >> 12],
+                                        hex_chars[(lo >> 8) & 15],
+                                        hex_chars[(lo >> 4) & 15],
+                                        hex_chars[lo & 15],
+                                        '\\',
+                                        'u',
+                                        hex_chars[hi >> 12],
+                                        hex_chars[(hi >> 8) & 15],
+                                        hex_chars[(hi >> 4) & 15],
+                                        hex_chars[hi & 15],
+                                    });
                                 },
                             }
                         },
diff --git a/test/transpiler/runtime-transpiler.test.ts b/test/transpiler/runtime-transpiler.test.ts
index 23e972be4..9aaca74fe 100644
--- a/test/transpiler/runtime-transpiler.test.ts
+++ b/test/transpiler/runtime-transpiler.test.ts
@@ -1,6 +1,15 @@
 import { beforeEach, describe, expect, test } from "bun:test";
 import { bunEnv, bunExe } from "harness";
 
+test("non-ascii regexp literals", () => {
+  var str = "🔴11 54 / 10,000";
+  expect(str.replace(/[🔵🔴,]+/g, "")).toBe("11 54 / 10000");
+});
+
+test("ascii regex with escapes", () => {
+  expect(/^[-#!$@£%^&*()_+|~=`{}\[\]:";'<>?,.\/ ]$/).toBeInstanceOf(RegExp);
+});
+
 describe("// @bun", () => {
   beforeEach(() => {
     delete require.cache[require.resolve("./async-transpiler-entry")];