完成/后处理链接方法

Question

Assuming I have an Array-like object which allows for chaining methods like so:

var ds = new DataSet(items);
var subset = ds.filter(condition1).filter(condition2);

Is there a way to execute code after the last method in the chain has been processed - without resorting to manually appending a separate .finalize() (or end / execute /...) method call?

I believe I've seen this before somewhere, but I don't recall the details. Perhaps futures/promises/deferreds would be of use here - but I don't really know how, since I always end up with the need to "look into the future" to determine whether a method call is the last in the chain.

Answer 1

If you control the filter method, it may be an idea to add a finalize parameter?

.filter(condition,[some finalizer function]);

in filter :

if (finalizer){
   finalizer();
}

[ edit based on comment ]

Another approach could be to allow for a finalizer condition, so in .filter(condition) , the contents of condition defines the need to finalize.

Something like (I don't know the type of your condition, just making things up):

if (condition.match('f=true')) {
  finalizer();
}