The source analysis of MaxAge blind spot of Lru-cache

Copy an example below

VarLru=Require"Lru-cache= {max: 500, lengthfunction (n, key) {return n * 2 +  Key. length}, dispose: function (key, n) {n.close ()}, MaxAge1000 * 60 * 60}, Cache = LRU (options) 
 
      

I'm supposed to be familiar with this part of you. MaxAge This parameter is very easy to misleading, here I detailed the maxAge. I always thought that when the set is over a key-value, the LRU will automatically delete the key-value when it exceeds the value set by MaxAge. However, after some analysis, the fact is not true ~

First MaxAge This parameter is verified only when the set value and the status are judged (Isstale method).

And Isstale This method is useful in the value, the judging value and the method foreach

Expired (more than maxage) values are removed by the Del method, and the Execute instance object is the Dispose method that is set when the execution is deleted.

Therefore, the MaxAge parameter value is valid, but the time check is performed when the get and ForEach are executed. Timeout executes the Dispose method.

The value of the Key-value can be taken for the timeout, depending on the stale parameter of the setting.

Parameter maxAge, stale parameter default

When get is judged whether to timeout, if timeout, return undefined after deletion

Parameter MaxAge, stale set true

When the get is determined whether to timeout, if the time-out, after the deletion of the value returned

The source analysis of MaxAge blind spot of Lru-cache