what will be the output of this javascript code setImmediate(() => console.log(1));

setTimeout(() => console.log(9), 0);

Promise.resolve().then(() => console.log(2));

process.nextTick(() => console.log(3));

fs.readFile(\_\_filename, () => {
 console.log(4);

 setTimeout(() => console.log(5), 0); // why set time out prints after setimmediate
 setImmediate(() => console.log(6));
 process.nextTick(() => console.log(7));
});

console.log(8);
To understand the output of the provided JavaScript code, we need to analyze the order of execution based on the Node.js event loop, which prioritizes different types of callbacks in the following order:

1. **Microtasks** (e.g., promises and `process.nextTick`)
2. **Timers** (e.g., `setTimeout` and `setInterval`)
3. **I/O callbacks** (e.g., `fs.readFile`, network operations, etc.)
4. **`setImmediate`**

Now, let's break down the provided code step by step:

1. **`setImmediate(() => console.log(1));`** - This schedules a callback to be executed in the next iteration of the event loop after the current operation completes.

2. **`setTimeout(() => console.log(9), 0);`** - This schedules a timeout with a delay of 0 milliseconds, which means it will be executed as soon as the current stack is clear and after all microtasks.

3. **`Promise.resolve().then(() => console.log(2));`** - This creates a resolved promise and schedules its `.then` callback, which is a microtask, to be executed after the current operation completes.

4. **`process.nextTick(() => console.log(3));`** - This schedules a callback to be executed in the current phase of the event loop, before any I/O tasks or microtasks.

5. **`fs.readFile(__filename
  The output of the code will be:

1
9
2
3
4
5
6
7
8

Explanation:

1. `setImmediate(() => console.log(1))`: This will log `1` to the console immediately, as the `setImmediate` function is a way to schedule a task to be executed later, but it will still be executed before any other tasks that are scheduled after it.
2. `setTimeout(() => console.log(9), 0)`: This will log `9` to the console after 0 milliseconds (i.e., immediately).
3. `Promise.resolve().then(() => console.log(2))`: This will log `2` to the console after the promise is resolved.
4. `process.nextTick(() => console.log(3))`: This will log `3` to the console after the next tick of the event loop.
5. `fs.readFile(_filename, () => { console.log(4); setTimeout(() => console.log(5), 0); setImmediate(() => console.log(6)); process.nextTick(() => console.log(7)); });`: This will log `4` to the console after the file is read, then log `5` to the console after 0 milliseconds (i.e., immediately),