nodejs: run long command several times

I have a command that I need to execute three times. It generates lots of output to stdout and takes about a minute. After the three commands finish, a fourth (different) command should be executed. A shell script would look like this:

#!/bin/sh
command arg1 arg2
command arg1 arg2
command arg1 arg2
something_else

I was thinking about using child_process.exec() in a loop but that buffers the stdout until it is finished (right?). I need to give the user immediate feedback so buffering the stdout for more than a second is not a good idea. So I need to use child_process.spawn() but the asynchronous handling drives me a bit nuts. I was thinking about putting the spawn call in a function like this:

fucnction myfunc(runs) {
   if (runs >= 1) {
       myproc = spawn(...)
       myproc.on('exit',function() { myfunc(runs - 1) })
   }
}

which would work I assume. But is there a better way? I am on unix and perhaps windows systems.