1 files changed, 34 insertions, 0 deletions
diff --git a/src/bun.js/bindings/bindings.cpp b/src/bun.js/bindings/bindings.cpp
index d06e8259e..a61a0221a 100644
--- a/src/bun.js/bindings/bindings.cpp
+++ b/src/bun.js/bindings/bindings.cpp
@@ -4689,6 +4689,40 @@ extern "C" EncodedJSValue JSC__JSValue__dateInstanceFromNullTerminatedString(JSC
     return JSValue::encode(date);
 }
 
+// this is largely copied from dateProtoFuncToISOString
+extern "C" int JSC__JSValue__toISOString(JSC::JSGlobalObject* globalObject, EncodedJSValue dateValue, char buffer[28])
+{
+    JSC::DateInstance* thisDateObj = JSC::jsDynamicCast<JSC::DateInstance*>(JSC::JSValue::decode(dateValue));
+    if (!thisDateObj)
+        return -1;
+
+    if (!std::isfinite(thisDateObj->internalNumber()))
+        return -1;
+
+    auto& vm = globalObject->vm();
+
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(vm.dateCache);
+    if (!gregorianDateTime)
+        return -1;
+
+    // If the year is outside the bounds of 0 and 9999 inclusive we want to use the extended year format (ES 15.9.1.15.1).
+    int ms = static_cast<int>(fmod(thisDateObj->internalNumber(), msPerSecond));
+    if (ms < 0)
+        ms += msPerSecond;
+
+    int charactersWritten;
+    if (gregorianDateTime->year() > 9999 || gregorianDateTime->year() < 0)
+        charactersWritten = snprintf(buffer, sizeof(buffer), "%+07d-%02d-%02dT%02d:%02d:%02d.%03dZ", gregorianDateTime->year(), gregorianDateTime->month() + 1, gregorianDateTime->monthDay(), gregorianDateTime->hour(), gregorianDateTime->minute(), gregorianDateTime->second(), ms);
+    else
+        charactersWritten = snprintf(buffer, sizeof(buffer), "%04d-%02d-%02dT%02d:%02d:%02d.%03dZ", gregorianDateTime->year(), gregorianDateTime->month() + 1, gregorianDateTime->monthDay(), gregorianDateTime->hour(), gregorianDateTime->minute(), gregorianDateTime->second(), ms);
+
+    ASSERT(charactersWritten > 0 && static_cast<unsigned>(charactersWritten) < sizeof(buffer));
+    if (static_cast<unsigned>(charactersWritten) >= sizeof(buffer))
+        return -1;
+
+    return charactersWritten;
+}
+
 #pragma mark - WebCore::DOMFormData
 
 CPP_DECL void WebCore__DOMFormData__append(WebCore__DOMFormData* arg0, ZigString* arg1, ZigString* arg2)