Node.js: timing functions

In my previous posts, I explained how node.js works asynchronously using even listeners, call backs. There is another way to work asynchronously using timing functions.

a.   setTimeout(callback, delay[, ...args])

b.   setInterval(callback, delay[, ...args])

setTimeout(callback, delay[, ...args])

Callback function is called when the timer elapses.

Below table summarizes the arguments of setTimeout method.

Argument	Description
Callback	Function to call when the timer elapses
Delay	Number of milliseconds to wait before calling callback function
args	Optional arguments to pass when the callback is called.

Let me explain with an example.

HelloWorld.js

var timeout = 3000; //3 seconds

setTimeout(function(){
 console.log("Hello, I woke up after 3 seconds");
}, timeout);

console.log("Reached End");

Output

Reached End

Hello, I woke up after 3 seconds

In the above example, callback function is called after 3 seconds.

Points to note

a. When delay is larger than 2147483647 or less than 1, the delay will be set to 1.

b. If callback is not a function, a TypeError will be thrown.

Passing parameters to setTimeout function

By using Optional arguments, you can pass arguments to the callback when it is called.

HelloWorld.js

var timeout = 3000; // 3 seconds

/* Function reference to a callback function */
var funRef = function(arg1, arg2) {
 console.log("Hello, I woke up after 3 seconds");
 console.log("Arguments passed : %s, %s", arg1, arg2);
};

/* funRef is called after 3 seconds and pass the optional arguments to funRef */
setTimeout(funRef, timeout, "Demo of setTimeout by", "Krishna");

console.log("Reached End");

Output

Reached End

Hello, I woke up after 3 seconds

Arguments passed : Demo of setTimeout by, Krishna

Clear the timeout

‘clearTimeout(timeout)’ method cancels a Timeout object created by setTimeout().

HelloWorld.js

var timeout = 3000; // 3 seconds

var timeout = setTimeout(function(){
 console.log("I woke up after 3 seconds...");
}, timeout);

console.log("Clearing the time out");

clearTimeout(timeout);

Output

Clearing the time out

setInterval(callback, delay[, ...args])

setInterval function is used to repeat the callback function for every delay milliseconds.

Below table summarizes the arguments of setInterval function.

Argument	Description
callback	Function to call when the timer elapses.
delay	Number of milliseconds to wait before calling callback
args	Optional arguments to pass, when the callback is called.

Let me explain with an example.

HelloWorld.js

var interval_time_out = 500;

setInterval(function(){
 console.log("Hi, I am here");
}, interval_time_out);

Output

Hi, I am here
Hi, I am here
Hi, I am here
Hi, I am here
Hi, I am here
Hi, I am here
Hi, I am here
Hi, I am here
……
……
……

Message ‘Hi, I am here’ is printed for every 500 milliseconds.

Pass arguments to callback function

By using Optional arguments, you can pass arguments to the callback when it is called.

HelloWorld.js

var interval_time_out = 500;

/* Function reference to a callback function */
var funRef = function(arg1, arg2) {
 console.log("Hello, I woke up every 500 milli seconds");
 console.log("Arguments passed : %s, %s", arg1, arg2);
};

setInterval(funRef, interval_time_out, "Demo of setInterval by", "Krishna");

Output

Hello, I woke up every 500 milli seconds
Arguments passed : Demo of setInterval by, Krishna
Hello, I woke up every 500 milli seconds
Arguments passed : Demo of setInterval by, Krishna
Hello, I woke up every 500 milli seconds
Arguments passed : Demo of setInterval by, Krishna
Hello, I woke up every 500 milli seconds
Arguments passed : Demo of setInterval by, Krishna
Hello, I woke up every 500 milli seconds
Arguments passed : Demo of setInterval by, Krishna
Hello, I woke up every 500 milli seconds
Arguments passed : Demo of setInterval by, Krishna
...........
...........
...........

Points to Note:

a. When delay is larger than 2147483647 or less than 1, the delay will be set to 1.

b. If callback is not a function, a TypeError will be thrown.

clearInterval(timeout): Cancel the setInterval

clearInterval(timeout) method is used to cancels a Timeout object created by setInterval().

HelloWorld.js

var interval_time_out = 500;
var interval_cancellation_time_out = 2000;

var intervalRef = setInterval(function(){
 console.log("Hi, I am here");
}, interval_time_out);

setTimeout(function(){
 clearInterval(intervalRef);
 console.log("Cancelled the interval timer");
}, interval_cancellation_time_out);

Output

Hi, I am here
Hi, I am here
Hi, I am here
Cancelled the interval timer

Previous                                                 Next                                                 Home