diff --git a/js/src/jsarray.cpp b/js/src/jsarray.cpp
index 24a552e2de6..75764cb33c9 100644
--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -1296,6 +1296,8 @@ Class js::ArrayClass = {
         array_getGeneric,
         array_getProperty,
         array_getElement,
+        NULL, /* getElementIfPresent, because this is hard for now for
+                 slow arrays */
         array_getSpecial,
         array_setGeneric,
         array_setProperty,
diff --git a/js/src/jsclass.h b/js/src/jsclass.h
index a2a8a843041..674a4d8591a 100644
--- a/js/src/jsclass.h
+++ b/js/src/jsclass.h
@@ -208,6 +208,8 @@ typedef JSBool
 typedef JSBool
 (* ElementIdOp)(JSContext *cx, JSObject *obj, JSObject *receiver, uint32 index, Value *vp);
 typedef JSBool
+(* ElementIfPresentOp)(JSContext *cx, JSObject *obj, JSObject *receiver, uint32 index, Value *vp, bool* present);
+typedef JSBool
 (* SpecialIdOp)(JSContext *cx, JSObject *obj, JSObject *receiver, SpecialId sid, Value *vp);
 typedef JSBool
 (* StrictGenericIdOp)(JSContext *cx, JSObject *obj, jsid id, Value *vp, JSBool strict);
@@ -313,6 +315,7 @@ struct ObjectOps
     GenericIdOp         getGeneric;
     PropertyIdOp        getProperty;
     ElementIdOp         getElement;
+    ElementIfPresentOp  getElementIfPresent; /* can be null */
     SpecialIdOp         getSpecial;
     StrictGenericIdOp   setGeneric;
     StrictPropertyIdOp  setProperty;
@@ -341,7 +344,7 @@ struct ObjectOps
 #define JS_NULL_OBJECT_OPS                                                    \
     {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,   \
      NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,   \
-     NULL,NULL,NULL,NULL,NULL}
+     NULL,NULL,NULL,NULL,NULL,NULL}
 
 struct Class
 {
diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index 0842417808f..8b240da5a9b 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -3457,6 +3457,7 @@ Class js::WithClass = {
         with_GetGeneric,
         with_GetProperty,
         with_GetElement,
+        NULL,             /* getElementIfPresent */
         with_GetSpecial,
         with_SetGeneric,
         with_SetProperty,
diff --git a/js/src/jsobjinlines.h b/js/src/jsobjinlines.h
index 4e4ae74a239..1611a41b1e8 100644
--- a/js/src/jsobjinlines.h
+++ b/js/src/jsobjinlines.h
@@ -1258,6 +1258,10 @@ inline JSBool
 JSObject::getElementIfPresent(JSContext *cx, JSObject *receiver, uint32 index, js::Value *vp,
                               bool *present)
 {
+    js::ElementIfPresentOp op = getOps()->getElementIfPresent;
+    if (op)
+        return op(cx, this, receiver, index, vp, present);
+
     /* For now, do the index-to-id conversion just once, then use
      * lookupGeneric/getGeneric.  Once lookupElement and getElement stop both
      * doing index-to-id conversions, we can use those here.
diff --git a/js/src/jsproxy.cpp b/js/src/jsproxy.cpp
index bba8d71f48f..ad454c48a37 100644
--- a/js/src/jsproxy.cpp
+++ b/js/src/jsproxy.cpp
@@ -139,6 +139,24 @@ ProxyHandler::get(JSContext *cx, JSObject *proxy, JSObject *receiver, jsid id, V
     return CallJSPropertyOp(cx, desc.getter, receiver, id, vp);
 }
 
+bool
+ProxyHandler::getElementIfPresent(JSContext *cx, JSObject *proxy, JSObject *receiver, uint32 index, Value *vp, bool *present)
+{
+    jsid id;
+    if (!IndexToId(cx, index, &id))
+        return false;
+
+    if (!has(cx, proxy, id, present))
+        return false;
+
+    if (!*present) {
+        Debug_SetValueRangeToCrashOnTouch(vp, 1);
+        return true;
+    }
+
+    return get(cx, proxy, receiver, id, vp);
+}   
+
 bool
 ProxyHandler::set(JSContext *cx, JSObject *proxy, JSObject *receiver, jsid id, bool strict,
                   Value *vp)
@@ -809,6 +827,15 @@ Proxy::get(JSContext *cx, JSObject *proxy, JSObject *receiver, jsid id, Value *v
     return GetProxyHandler(proxy)->get(cx, proxy, receiver, id, vp);
 }
 
+bool
+Proxy::getElementIfPresent(JSContext *cx, JSObject *proxy, JSObject *receiver, uint32 index,
+                           Value *vp, bool *present)
+{
+    JS_CHECK_RECURSION(cx, return false);
+    AutoPendingProxyOperation pending(cx, proxy);
+    return GetProxyHandler(proxy)->getElementIfPresent(cx, proxy, receiver, index, vp, present);
+}
+
 bool
 Proxy::set(JSContext *cx, JSObject *proxy, JSObject *receiver, jsid id, bool strict, Value *vp)
 {
@@ -1017,6 +1044,13 @@ proxy_GetElement(JSContext *cx, JSObject *obj, JSObject *receiver, uint32 index,
     return proxy_GetGeneric(cx, obj, receiver, id, vp);
 }
 
+static JSBool
+proxy_GetElementIfPresent(JSContext *cx, JSObject *obj, JSObject *receiver, uint32 index,
+                          Value *vp, bool *present)
+{
+    return Proxy::getElementIfPresent(cx, obj, receiver, index, vp, present);
+}
+
 static JSBool
 proxy_GetSpecial(JSContext *cx, JSObject *obj, JSObject *receiver, SpecialId sid, Value *vp)
 {
@@ -1251,6 +1285,7 @@ JS_FRIEND_DATA(Class) js::ObjectProxyClass = {
         proxy_GetGeneric,
         proxy_GetProperty,
         proxy_GetElement,
+        proxy_GetElementIfPresent,
         proxy_GetSpecial,
         proxy_SetGeneric,
         proxy_SetProperty,
@@ -1312,6 +1347,7 @@ JS_FRIEND_DATA(Class) js::OuterWindowProxyClass = {
         proxy_GetGeneric,
         proxy_GetProperty,
         proxy_GetElement,
+        proxy_GetElementIfPresent,
         proxy_GetSpecial,
         proxy_SetGeneric,
         proxy_SetProperty,
@@ -1385,6 +1421,7 @@ JS_FRIEND_DATA(Class) js::FunctionProxyClass = {
         proxy_GetGeneric,
         proxy_GetProperty,
         proxy_GetElement,
+        proxy_GetElementIfPresent,
         proxy_GetSpecial,
         proxy_SetGeneric,
         proxy_SetProperty,
diff --git a/js/src/jsproxy.h b/js/src/jsproxy.h
index 2fcf214d46d..2f3b374f3ba 100644
--- a/js/src/jsproxy.h
+++ b/js/src/jsproxy.h
@@ -88,6 +88,8 @@ class JS_FRIEND_API(ProxyHandler) {
     virtual bool defaultValue(JSContext *cx, JSObject *obj, JSType hint, Value *vp);
     virtual void finalize(JSContext *cx, JSObject *proxy);
     virtual void trace(JSTracer *trc, JSObject *proxy);
+    virtual bool getElementIfPresent(JSContext *cx, JSObject *obj, JSObject *receiver,
+                                     uint32 index, Value *vp, bool *present);
 
     virtual bool isOuterWindow() {
         return false;
@@ -120,6 +122,8 @@ class Proxy {
     static bool has(JSContext *cx, JSObject *proxy, jsid id, bool *bp);
     static bool hasOwn(JSContext *cx, JSObject *proxy, jsid id, bool *bp);
     static bool get(JSContext *cx, JSObject *proxy, JSObject *receiver, jsid id, Value *vp);
+    static bool getElementIfPresent(JSContext *cx, JSObject *proxy, JSObject *receiver,
+                                    uint32 index, Value *vp, bool *present);
     static bool set(JSContext *cx, JSObject *proxy, JSObject *receiver, jsid id, bool strict,
                     Value *vp);
     static bool keys(JSContext *cx, JSObject *proxy, AutoIdVector &props);
diff --git a/js/src/jstypedarray.cpp b/js/src/jstypedarray.cpp
index 56b8a3c25fb..a63e036b632 100644
--- a/js/src/jstypedarray.cpp
+++ b/js/src/jstypedarray.cpp
@@ -2105,6 +2105,7 @@ Class js::ArrayBufferClass = {
         ArrayBuffer::obj_getGeneric,
         ArrayBuffer::obj_getProperty,
         ArrayBuffer::obj_getElement,
+        NULL, /* getElementIfPresent */
         ArrayBuffer::obj_getSpecial,
         ArrayBuffer::obj_setGeneric,
         ArrayBuffer::obj_setProperty,
@@ -2217,6 +2218,7 @@ JSFunctionSpec _typedArray::jsfuncs[] = {                                      \
         _typedArray::obj_getGeneric,                                           \
         _typedArray::obj_getProperty,                                          \
         _typedArray::obj_getElement,                                           \
+        NULL, /* getElementIfPresent */                                        \
         _typedArray::obj_getSpecial,                                           \
         _typedArray::obj_setGeneric,                                           \
         _typedArray::obj_setProperty,                                          \
diff --git a/js/src/jsxml.cpp b/js/src/jsxml.cpp
index 0dd1babcbf9..c9873505547 100644
--- a/js/src/jsxml.cpp
+++ b/js/src/jsxml.cpp
@@ -5361,6 +5361,7 @@ JS_FRIEND_DATA(Class) js::XMLClass = {
         xml_getGeneric,
         xml_getProperty,
         xml_getElement,
+        NULL, /* getElementIfPresent */
         xml_getSpecial,
         xml_setGeneric,
         xml_setProperty,
diff --git a/js/xpconnect/src/XPCWrappedNativeJSOps.cpp b/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
index 4e185e5c317..b1e3864d2a5 100644
--- a/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
+++ b/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
@@ -866,6 +866,7 @@ js::Class XPC_WN_NoHelper_JSClass = {
         nsnull, // getGeneric
         nsnull, // getProperty
         nsnull, // getElement
+        nsnull, // getElementIfPresent
         nsnull, // getSpecial
         nsnull, // setGeneric
         nsnull, // setProperty
diff --git a/js/xpconnect/src/xpcprivate.h b/js/xpconnect/src/xpcprivate.h
index c006b7e4b7e..8bc15d22157 100644
--- a/js/xpconnect/src/xpcprivate.h
+++ b/js/xpconnect/src/xpcprivate.h
@@ -1407,6 +1407,7 @@ XPC_WN_JSOp_ThisObject(JSContext *cx, JSObject *obj);
         nsnull, /* getGeneric    */                                           \
         nsnull, /* getProperty    */                                          \
         nsnull, /* getElement    */                                           \
+        nsnull, /* getElementIfPresent */                                     \
         nsnull, /* getSpecial    */                                           \
         nsnull, /* setGeneric    */                                           \
         nsnull, /* setProperty    */                                          \
@@ -1444,6 +1445,7 @@ XPC_WN_JSOp_ThisObject(JSContext *cx, JSObject *obj);
         nsnull, /* getGeneric    */                                           \
         nsnull, /* getProperty    */                                          \
         nsnull, /* getElement    */                                           \
+        nsnull, /* getElementIfPresent */                                     \
         nsnull, /* getSpecial    */                                           \
         nsnull, /* setGeneric    */                                           \
         nsnull, /* setProperty    */                                          \