Proxy object allows developers to proxyfy an object. All traps in the handler are optional, but starting with Firefox 21, proxyfied arrays without the
get trap are not working properly. If the
get trap is not defined,
0 and the
set trap doesn’t get called. A workaround is to add the no-op
get trap even if it’s not necessary in your code.
Update: This issue has been fixed with Firefox 40.