How to create a sleep/delay in nodejs that is Blocking?

Question

I'm currently trying to learn nodejs and a small project I'm working is writing an API to control some networked LED lights.

The microprocessor controlling the LEDs has a processing delay, and I need to space commands sent to the micro at least 100ms apart. In C# I'm used to just calling Thread.Sleep(time), but I have not found a similar feature in node.

I have found several solutions using the setTimeout(...) function in node, however, this is asynchronous and does not block the thread ( which is what I need in this scenario).

Is anyone aware of a blocking sleep or delay function? Preferably something that does not just spin the CPU, and has an accuracy of +-10 ms?

Answer 1

Node is asynchronous by nature, and that's what's great about it, so you really shouldn't be blocking the thread, but as this seems to be for a project controlling LED's, I'll post a workaraound anyway, even if it's not a very good one and shouldn't be used (seriously).

A while loop will block the thread, so you can create your own sleep function

function sleep(time, callback) {     var stop = new Date().getTime();     while(new Date().getTime() < stop + time) {         ;     }     callback(); } 

to be used as

sleep(1000, function() {    // executes after one second, and blocks the thread }); 

I think this is the only way to block the thread (in principle), keeping it busy in a loop, as Node doesn't have any blocking functionality built in, as it would sorta defeat the purpose of the async behaviour.

Answer 2

With ECMA script 2017 (supported by Node 7.6 and above), it becomes a one-liner:

function sleep(millis) {   return new Promise(resolve => setTimeout(resolve, millis)); }  // Usage in async function async function test() {   await sleep(1000)   console.log("one second has elapsed") }  // Usage in normal function function test2() {   sleep(1000).then(() => {     console.log("one second has elapsed")   }); }