sleep.md

Module: sleep

• Intro: sleep utility methods (for debugging)
• Type: 3rd-party
• Document: Node.js API Docs - sleep
• Requiring syntax: const sleep = require('sleep');

Notes

blocking 式的 sleep，和 setTimeout() 的 callback 式不同，主要用於 debugging

Abstract from docs:

• Add sleep(), msleep() and usleep() to Node.js, via a C++ binding.
• This is mainly useful for debugging.
• These calls will block execution of all JavaScript by halting Node.js' event loop!

TOC

• sleep.sleep(n): sleep for n seconds
• sleep.msleep(n): sleep for n miliseconds
• sleep.usleep(n): sleep for n microseconds (1 second is 1000000 microseconds)
• sleep.sleep() vs. setTimeout()

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sleep.sleep(n), sleep.msleep(n), sleep.usleep(n)

Example:

console.log('app start');

const sleep = require('sleep');
sleep.sleep(5);

console.log('app end');

Result:

app start
(pause 5 secs here)
app end

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sleep.sleep() vs. setTimeout()

由於 setTimeout() 是 callback queue，會等到 main call stack 結束才執行。

Example:

console.log('app start');

setTimeout( () => {
    console.log('Inside of callback 1');
}, 2000); //milliseconds

setTimeout( () => {
    console.log('Inside of callback 2');
}, 0);

console.log('break point 1');

const sleep = require('sleep');
sleep.sleep(5);

console.log('app end');

Result:

app start
break point 1
(pause 5 secs here)
app end
Inside of callback 2
Inside of callback 1