Redis scan javascript promise (when) example

redis-scan-promise-iterate.js

var count = 0;

when.iterate(function(args) {
    var cursor = parseInt(args[0]);
    return redis.whenZScan('mykey', cursor || 0);
}, function predicate(args) {
    var cursor = parseInt(args[0]);
    return cursor === 0;
}, function handler(args) {
    if (args.length > 1) {
        var images = args[1];
        count += images.length / 2; // because score follows key
    }
}, [null])
.then(function() {
    console.log('Done. count:', count);
});