It seems almost all the time node.js runs hello world is spent loading its own modules. You should try something like this: // watch.js var file = proc

It seems almost all the time node.js runs hello world is spent loading its own modules. You should try something like this: // watch.js var file = process.argv[2] console.log('press enter to run '+file) process.stdin.on('data', function(){ var [s1,ns1] = process.hrtime() for(var k in require.cache) { delete require.cache[k] } require(file) var [s2,ns2] = process.hrtime() var s = (s2-s1)+(ns2-ns1)*1e-9 console.log('time: ' + s.toFixed(9)) }) Result: less than 1ms on first run $ node watch.js ./test.js press enter to run ./test.js hello world time: 0.000952656 hello world time: 0.000284171 edit: script now deletes all cache, not only the passed script (result is the same if the script doesn't require others)