inflight
Add callbacks to requests in flight to avoid async duplication
USAGE
var inflight = // some request that does some stuff { // key is any random string. like a url or filename or whatever. // // will return either a falsey value, indicating that the // request for this key is already in flight, or a new callback // which when called will call all callbacks passed to inflightk // with the same key callback = // If we got a falsey value back, then there's already a req going if !callback return // this is where you'd fetch the url or whatever // callback is also once()-ified, so it can safely be assigned // to multiple events etc. First call wins. } // only assigns a single setTimeout// when it dings, all cbs get called