执行哪些事件循环阶段事件发射器回调？

问：

我已经开始学习节点事件循环，根据我的理解，除了回调之外，所有回调都会分阶段执行，但是当检查事件发射器回调时，它会在每个阶段执行，比如下面的代码setInterval, setImmediate, setTimeoutpoll

const EventEmitter = require('events');
const fs = require('fs');

const eventEmitter = new EventEmitter();
eventEmitter.on('emit', (eventName) => {
  console.log('<----- an event occurred! --->', eventName);
});

setTimeout(() => {
  setTimeout(() => {
    console.log(' setTimeout 0');
    eventEmitter.emit('emit', 'emit inside setTimeout 0');
  }, 0);

  setTimeout(() => {
    console.log(' setTimeout 5');
    eventEmitter.emit('emit', 'setInterval inside setTimeout 5');
  }, 5);

  process.nextTick(() => {
    console.log('process.nextTick');
    eventEmitter.emit('emit', 'emit inside process.nextTick');
  });

  Promise.resolve().then(() => {
    console.log('Promise.resolve()');
    eventEmitter.emit('emit', 'emit inside Promise.resolve()');
  });

  setImmediate(() => {
    console.log('setImmediate');
    eventEmitter.emit('emit', 'emit inside setImmediate 1');
  });

  fs.readFile(__filename, () => {
    console.log('fs.readFile');
    eventEmitter.emit('emit', 'emit inside fs.readFile');
  });


console.log('sync');
}, 0)

如果我打印输出，它如下所示

sync
process.nextTick
<----- an event occurred! ---> emit inside process.nextTick
Promise.resolve()
<----- an event occurred! ---> emit inside Promise.resolve()
setImmediate
<----- an event occurred! ---> emit inside setImmediate 1
setTimeout 0
<----- an event occurred! ---> emit inside setTimeout 0
setTimeout 5
<----- an event occurred! ---> setInterval inside setTimeout 5
fs.readFile
<----- an event occurred! ---> emit inside fs.readFile

一旦每个阶段都发出事件，这个事件发射器回调是如何执行的？