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, allKeys) {
    var keyTypes = {};

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