Asynchronous programming in Nodejs
Posted By : Ritik Jain | 15-Jan-2021
The Classical Approach - Callbacks
Let us explore these simple async operations. Here, the operation is to just start a timer, and at the end of the timer call a function.
function fastFunction (done) {
setTimeout(function () {
done()
}, 100)
}
function slowFunction (done) {
setTimeout(function () {
done()
}, 300)
}
Also Read: How to Create Freshdesk Serverless App using Nodejs
Although we can execute the higher-order functions either sequentially or in parallel with the basic "pattern" by nesting callbacks, however, the method can result in an untameable callback-hell.
function runSequentially (callback) {
fastFunction((err, data) => {
if (err) return callback(err)
console.log(data) // results of a
slowFunction((err, data) => {
if (err) return callback(err)
console.log(data) // results of b
// here you can continue running more tasks
})
})
}
Also Read: Using a template engine in Nodejs
To handle this issue, we need to use the following approaches:-
Using Promises
function fastFunction () {
return new Promise((resolve, reject) => {
setTimeout(function () {
console.log('Fast function done')
resolve()
}, 100)
})
}
function slowFunction () {
return new Promise((resolve, reject) => {
setTimeout(function () {
console.log('Slow function done')
resolve()
}, 300)
})
}
function asyncRunner () {
return Promise.all([slowFunction(), fastFunction()])
}
Using async and await
function scaryClown() {
return new Promise(resolve => {
setTimeout(() => {
resolve('??');
}, 2000);
});
}
async function msg() {
const msg = await scaryClown();
console.log('Message:', msg);
}
msg();
Thanks for reading.
Also Read: Using The Microservices and NodeJS
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About Author
Ritik Jain
Ritik is an accomplished Backend Developer with extensive experience in Mean. He is proficient in Core Java, Spring-Boot, Hibernate, Node.js, Angular 2+, and various relational databases like MySQL and MongoDB. With his expertise in API implementations, webservices, development testing, and deployments, he has contributed to the successful completion of various client projects. Apart from his professional pursuits, Ritik is an enthusiastic gamer and keeps himself updated with the latest advancements in technology.