The Smooth Operator
Cache the return value of an asynchronous function (callback-taking or promise-returning).
Optional: have it periodically refresh data in the background, and keep returning the latest until a new value replaces it. Especially useful with unreliable or slow sources.
smoop(fn, opts) -> fn'
Options
-
refresh
Milliseconds before proactively trying to fetch a new value. The current value is kept and handed out until replaced.
Without
refresh
you will get a lazy behavior where a new value is fetched only when needed.With
refresh
a value will initially be polled. -
maxAge
Milliseconds until a value is discarded.
If you do not set
maxAge
you are guaranteed to always get a value if any source has ever resolved.A
maxAge
of zero is the same as disabling the caching altogether. -
name
Smooth operator uses debug and assigns each operator a sequential number for referencing.
name
allows you to use your own reference.
Using node-style callbacks
var smoop = require('smoop');
var dns = require('dns');
var googleIp = smoop(function( cb ){
dns.lookup('google.com', cb);
}, {
refresh: 60000, // fetch each minute
});
googleIp(function( err, result ){
console.log('google.com address:', result[0]);
});
Using promises
var Promise = require('bluebird');
var smoop = require('smoop');
var dns = Promise.promisifyAll(require('dns'));
var googleIp = smoop(function(){
return dns.lookupAsync('google.com');
}, {
refresh: 60000, // fetch each minute
});
googleIp().spread(function( ip ){
console.log('google.com address:', ip);
});