process.nextTickとsetImmediateの違いを理解する

event_loop.js

'use strict';
var fs = require('fs');

console.log('start');

fs.readFile('./a.txt', function(err, data) {
  console.log('readFile');

  process.nextTick(function() {
    console.log('readFile -> nextTick');
  });

  setImmediate(function() {
    console.log('readFile -> setImmediate');
  });
});

process.nextTick(function() {
  console.log('nextTick');
  fs.readFile('./a.txt', function(err, data) {
    console.log('nextTick -> readFile');
  });
});

setImmediate(function() {
  console.log('setImmediate');
  fs.readFile('./a.txt', function(err, data) {
    console.log('setImmediate -> readFile');
  });
});

setTimeout(function() {
  console.log('setTimeout');
  fs.readFile('./a.txt', function(err, data) {
    console.log('setTimeout -> readFile');
  });
}, 0);

(function doNextTick(i) {
  console.log(`doNextTick ${i}`);
  if (i >= 10) {
    return;
  }
  i++;
  process.nextTick(function() {
    doNextTick(i);
  });
})(1);

(function doSetImmediate(i) {
  console.log(`doSetImmediate ${i}`);
  if (i >= 10) {
    return;
  }
  i++;
  setImmediate(function() {
    doSetImmediate(i);
  });
})(1);