JavaScript / Node.js event loop tick ids

Question

I am wondering if there is some neat way of knowing if a function is called in the current tick (the tick in which the function was declared), or the next tick (or some future tick) of the Node.js event loop

for example:

function foo(cb){

  // we can fire callback synchronously
  cb();

  // or we can fire callback asynchronously
  process.nextTick(cb);

}

say will call foo like so:

function outer(){

   const currentTickId = process.currentTickId;

  function bar(){          //bar gets created everytime outer is called..

    if(process.currentTickId === currentTickId){
       //do something
    }
    else{

     // do something else
    }


  }

  // foo is always called in the same tick that bar was
  // declared, but bar might not be called until the next tick

  foo(bar);  


}

most applications won't need something like this, but I am writing a library and it would be useful to have this functionality, if it's possible! note that process.currentTickId is made up by me for this example

Answer 1

It looks like you've already discovered process.nextTick.

You could use this to rig up a system to achieve "process.currentTickId" as the code in your question indicates you need:

process.currentTickId = 0;

const onTick = () => {
    process.currentTickId++;
    process.nextTick(onTick);
};

process.nextTick(onTick);