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);
});