node-redis/examples/subquery.js

'use strict';

var client = require('redis').createClient();

// build a map of all keys and their types
client.keys('*', function (err, all_keys) {
    var key_types = {};

    all_keys.forEach(function (key, pos) { // use second arg of forEach to get pos
        client.type(key, function (err, type) {
            key_types[key] = type;
            if (pos === all_keys.length - 1) { // callbacks all run in order
                console.dir(key_types);
            }
        });
    });
});