What is the difference between process.nextTick and setImmediate

Short answer

process.nextTick queues a callback to execute immediately after the current operation completes, before the event loop continues. setImmediate queues a callback to execute during the check phase of the next event loop iteration.

Key differences

• Priority: process.nextTick callbacks run before I/O events and timers. setImmediate runs after I/O events.
• Phase: nextTick is not technically part of the event loop; it is a separate microtask queue. setImmediate runs in the check phase.
• Usage: Use nextTick when you need to ensure a callback runs before any other asynchronous operation. Use setImmediate when you want to yield to the event loop.

When to use each

• Use process.nextTick for ensuring consistent API behavior before emitting events.
• Use setImmediate for deferring work to prevent starving the event loop with recursive nextTick calls.