index.js
function cleanup(key) {
    callbackQueue[key] = null;
    if (++nulls > nullThreshold) {
        callbackQueue = omit(callbackQueue, function removeNulls(datum) {
            return datum === null;
        });
    }
}
function cleanup(key) {
    callbackQueue[key] = null;
    if (++nulls > nullThreshold) {
        callbackQueue = omit(callbackQueue, function removeNulls(datum) {
            return datum === null;
        });
    }
}
function cleanup ( key ) { callbackQueue [ key ] = null ; if ( ++ nulls > nullThreshold ) { callbackQueue = omit ( callbackQueue , function removeNulls ( datum ) { return datum === null ; } ) ; } }
Performs cleanup on queue object
@param  {String} key
Performs cleanup on queue object