Explain clearTimeout() function in Node.js

In node.js, there exists a timer module that is used to schedule timers and execute some kind of functionality in some future time period.

JavaScript setTimeout() Method: It is used to schedule functionality to be executed after provided milliseconds, below is a simple example of setTimeout() method.

Example: The setTimeout inside the script tag is registering a function to be executed after 3000 milliseconds and inside the function, there is only an alert.

Javascript

function alertAfter3Seconds() {
    console.log("Hi, 3 Second completed!");
}
setTimeout(alertAfter3Seconds, 3000);

Output:

Hi, 3 Second completed!

JavaScript clearTimeout() Method: This method comes under the category of canceling timers and is used to cancel the timeout object created by setTimeout. The setTimeout() method also returns a unique timer id which is passed to clearTimeout to prevent the execution of the functionality registered by setTimeout. 

Example: Here we have stored the timer id returned by setTimeout, and later we are passing it to the clearTimeout method which immediately aborts the timer.

Javascript

function alertAfter3Seconds() {
    alert("Hi, 3 Second completed!");
}

const timerId = setTimeout(alertAfter3Seconds, 3000);

clearTimeout(timerId);
console.log("Timer has been Canceled");

Output: Here we will not be able to see that alert registered to be executed after 3000 milliseconds because clearTimeout canceled that timer object before execution.

Timer has been Canceled