output

ZokaMac:node Zoka$ ./node  ../sample/timer_test.js 1000
v8 delta: 100 msec  expected: 100 ms, v8_error: 0 ms
v8 delta: 1000 msec  expected: 1000 ms, v8_error: 0 ms

ZokaMac:node Zoka$ ./node  ../sample/timer_test.js 10000
v8 delta: 98 msec  expected: 100 ms, v8_error: 2 ms
v8 delta: 998 msec  expected: 1000 ms, v8_error: 2 ms

ZokaMac:node Zoka$ ./node  ../sample/timer_test.js 100000
v8 delta: 85 msec  expected: 100 ms, v8_error: 15 ms
v8 delta: 985 msec  expected: 1000 ms, v8_error: 15 ms

ZokaMac:node Zoka$ ./node  ../sample/timer_test.js 1000000
v8 delta: 1 msec  expected: 100 ms, v8_error: 99 ms
v8 delta: 859 msec  expected: 1000 ms, v8_error: 141 ms

timer_test.js

// timer_test.js

var sys=require('sys');


function test_timer_accuracy(expected) {
  var v8_ms        = Date.now();

  function interval_cb() {  
    var v8_ms_now        = Date.now();
  
    var v8_delta = v8_ms_now-v8_ms;
    var error = expected-v8_delta;
   
    sys.puts("v8 delta: "+v8_delta + " msec  expected: "+ expected + " ms, v8_error: "
      +error+" ms");   
  }
  setTimeout(interval_cb, expected);
}

var x;
var y = 0;
var n = 1000000;

if (process.argv.length > 2)
  n = process.argv[2];

for (x = 0; x < n; x++)
  y += x;  

test_timer_accuracy(100);
test_timer_accuracy(1000);