Your Web News in One Place

Help Webnuz

Referal links:

Sign up for GreenGeeks web hosting
December 22, 2021 02:16 pm GMT

Using Promise.race usefully

When doing long running tasks like :-

  1. DB query which may take long time
  2. Reading big files
  3. API which may take long time to complete
  4. Waiting for some event

You may want to stop if the task is taking more time than usual to get completed. In that case Promise.race can be useful.

Puppeteer project uses Promise.race to handle page/network lifecycle events with timeouts during automation.

Here's an example :-

/** * A utility function which throws error after timeout * @param timeout - timeout in seconds * @returns - promise which gets rejected after timeout */function timer(timeout) {    return new Promise((resolve, reject) => {        setTimeout(reject, timeout * 1000)    })}/** * Mock db query which take 5 seconds to complete * @returns - query promise */function bigQuery() {    return new Promise((resolve, reject) => {        setTimeout(resolve, 5 * 1000)    })}// race both bigQuery and timer tasks// `Promise.race` can take multiple promises if you want to race them allPromise.race([    bigQuery(),    timer(1)]).then(() => console.log(' Query successful within time limit'))    .catch(() => console.log(' Query failed with timeout'))// ==> will log ' Query failed with timeout'// also try running above code by changing timer's timeout value to 6 seconds, you will get successful log

You can play with the above code here :-

/**A utility function which throws error after timeout@param timeout - timeout in seconds@returns - promise which gets rejected after timeout*/function timer(timeout) {return new Promise((resolve, reject) => { setTimeout(reject, timeout * 1000)})}/**Mock db query which take 5 seconds to complete@returns - query promise*/function bigQuery() {return new Promise((resolve, reject) => { setTimeout(resolve, 5 * 1000)})}// race both bigQuery and timer tasks// Promise.race can take multiple promises if you want to race them allPromise.race([ bigQuery(), timer(1)]).then(() => console.log(' Query successful within time limit')) .catch(() => console.log(' Query failed with timeout'))// ==> will log ' Query failed with timeout'// also try running above code by changing timer's timeout value to 6 seconds, you will get successful log

Let me know in comments other cool ideas using Promise.race

See my projects on Github.


Original Link: https://dev.to/gajananpp/using-promiserace-usefully-420f

Share this article:    Share on Facebook
View Full Article

Dev To

An online community for sharing and discovering great ideas, having debates, and making friends

More About this Source Visit Dev To