Difference between process.nextTick() and setImmediate()?

What You'll Learn

How each function works
Execution order differences
When to use which

Key Difference

Feature	process.nextTick()	setImmediate()
Timing	Before event loop continues	After I/O in check phase
Queue	nextTick queue	Check phase queue
Recursion	Can block event loop	Won't block event loop

Execution Order

code.jsJavaScript

console.log('1: Start');

setImmediate(() => console.log('2: setImmediate'));

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

Promise.resolve().then(() => console.log('4: Promise'));

console.log('5: End');

// Output:
// 1: Start
// 5: End
// 3: nextTick
// 4: Promise
// 2: setImmediate

Priority Order

code.jsJavaScript

1. Synchronous code
2. process.nextTick()
3. Microtasks (Promises)
4. Macrotasks (setTimeout, setImmediate)

Warning: Recursive nextTick

code.jsJavaScript

// ❌ This will block the event loop!
function recursiveNextTick() {
  process.nextTick(recursiveNextTick);
}

// ✅ This won't block
function recursiveImmediate() {
  setImmediate(recursiveImmediate);
}

When to Use

nextTick: Execute before any I/O, cleanup after sync code
setImmediate: Execute after I/O, let event loop breathe