process.nexTick در مقابل setImmediate – انجمن DEV

Example


const fs = require('fs');

console.log('Start');

// Schedule with process.nextTick
process.nextTick(() => {
    console.log('Next Tick');
});

// Schedule with setImmediate
setImmediate(() => {
    console.log('Immediate');
});

// Read a file (simulates I/O operation)
fs.readFile(__filename, () => {
    console.log('File Read');

    // Schedule another nextTick inside I/O
    process.nextTick(() => {
        console.log('Next Tick inside I/O');
    });

    // Schedule another setImmediate inside I/O
    setImmediate(() => {
        console.log('Immediate inside I/O');
    });
});

console.log('End');

Expected Output

Start
End
Next Tick
File Read
Next Tick inside I/O
Immediate inside I/O
Immediate

Initial Phase:
    console.log('Start') is executed.
    process.nextTick(() => { console.log('Next Tick'); }) schedules a callback to be executed after the current phase.
    setImmediate(() => { console.log('Immediate'); }) schedules a callback for the next iteration of the event loop.
    fs.readFile(__filename, () => { ... }) schedules an I/O operation.

After Initial Phase:
    console.log('End') is executed.
    process.nextTick callback is executed: console.log('Next Tick').

I/O Phase:
    File read operation completes, console.log('File Read') is executed.
    Inside the I/O callback:
        process.nextTick(() => { console.log('Next Tick inside I/O'); }) schedules another callback for the current phase.
        setImmediate(() => { console.log('Immediate inside I/O'); }) schedules another callback for the next iteration of the event loop.
    process.nextTick callback inside I/O is executed: console.log('Next Tick inside I/O').

Next Event Loop Iteration:
    All setImmediate callbacks are executed in order: console.log('Immediate inside I/O') and console.log('Immediate').

process.nextTick executes the callback before the next I/O event.
setImmediate executes the callback after the current I/O events.