This code has the same effect as though the calls to capture were calls to fn.

Results

var queue = [];
function capture() {
    queue.push(Array.prototype.slice.call(arguments, 0));
}
function replay() {
    while (queue.length)
        fn.apply(null, queue.shift());
}
function fn(a, b) {
    log(a + ' + ' + b + ' = ' + (a+b));
}
capture(1,2);
capture(1,3);
capture(10,20);
replay();