Review
- 2024-08-13 08:00
[!Summary]
process.nextTick()在当前执行栈清空后，下一轮事件循环的「立即」执行阶段被调用，优先级最高。有自己的 nextTick Queue。属于特殊微任务。
一、Introduction #
Every time the event loop takes a full trip, we call it a tick.
When we pass a function to process.nextTick(), we instruct the engine to invoke this function at the end of the current operation, before the next event loop tick starts:
process.nextTick(() => {
// do something
});The event loop is busy processing the current function code. When this operation ends, the JS engine runs all the functions passed to nextTick calls during that operation.
It’s the way we can tell the JS engine to process a function asynchronously (after the current function), but as soon as possible, not queue it.
Calling setTimeout(() => {}, 0) will execute the function at the end of next tick, much later than when using nextTick() which prioritizes the call and executes it just before the beginning of the next tick.
Use nextTick() when you want to make sure that in the next event loop iteration that code is already executed.
console.log('Hello => number 1');
setImmediate(() => {
console.log('Running before the timeout => number 3');
});
setTimeout(() => {
console.log('The timeout running last => number 4');
}, 0);
process.nextTick(() => {
console.log('Running at next tick => number 2');
});Reference #
https://nodejs.org/en/learn/asynchronous-work/event-loop-timers-and-nexttick https://nodejs.org/en/learn/asynchronous-work/understanding-processnexttick