Synchronous Console Methods

In Node v0.10.x, the console functions are synchronous when the destination is a terminal or a file (to avoid lost messages in case of premature exit) and asynchronous when it’s a pipe (to avoid blocking for long periods of time). See console. We can test it with the following script:

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// Usage: `$ time node console.js`
var msg = '0';
var start;
for (var i = 0, len = 20; i < len; i+=1) {
  msg += msg;
}
process.on('exit', function (code) {
  console.log('Time elapsed: %d ms', Date.now() - start);
  console.log('Node', process.version);
});
start = Date.now();
console.log(msg);
console.log('Time elapsed: %d ms', Date.now() - start);

Run the script:

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$ time node console.js
Time elapsed: 2966 ms
Time elapsed: 2967 ms
Node v0.10.33
real    0m3.017s
user    0m0.052s
sys     0m0.000s

Switching to other methods such as console.error, the result will still be synchronous, as stated in API documentation.

However, if you are running Node v0.11.x branch, things are different:

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$ time node console.log
Time elapsed: 35 ms
Time elapsed: 2732 ms
Node v0.11.14
real    0m2.762s
user    0m0.040s
sys     0m0.012s

:)