Edit in JSFiddle

// setup

function finder(records, cb) {
    setTimeout(function () {
        records.push(3, 4);
        cb(records);
    }, 500);
}
function processor(records, cb) {
    setTimeout(function () {
        records.push(5, 6);
        cb(records);
    }, 500);
}

// using the callbacks
finder([1, 2], function (records) {
    processor(records, function(records) {
             console.log(records);       
    });
});

// or

function onProcessorDone(records){
    alert(records);   
}

function onFinderDone(records) {
    processor(records, onProcessorDone);
}

finder([1, 2], onFinderDone);