Undefined because the test function was expecting three inputs but two only were given and function declares third as undefined. In this case, console shows room 20 undefined printed to the console. Here, we told to wait for 20 seconds, That's the reason, we see output for 20 seconds. setInterval starts a function every n milliseconds, without any consideration about when a function finished its execution. SetTimeout(doSomething_JustOnce_AfterThisTime,20seconds): we are basically telling to do something just once after 20 seconds and the result of using this package in the above is: This is like saying to clap and stop at same time. Remember, executing these two codes one after another, it happens so quickly that we don't see any output at all. Below is the result we see if we execute above answers. SetInterval(clap_your_hands,5 seconds): we are basically telling what to do, that is, to clap once after every 5 secondsĬlearInterval(stop_clapping): we are basically telling to clear what we were doing, stop clapping task and do nothing.Īll above answers have talked about these two packages but there in one big flaw. The setInterval() method continues calling the function until clearInterval. Task: give a clap once every 5 seconds and stop doing this after 20 seconds. The setInterval() method calls a function at specified intervals (in milliseconds). You can use one terminal to execute a Node.js file. We are not covering it here as the installation process is different for a different operating system. If not, you can download and install it from here. I am not able to clearInterval any more : clearInterval(user.intervalid) // does not work setInterval () Let’s check them one by one: Create a Node.js file: I am assuming that you have Node.js installed on your system. When I attach interval to an existing user object, example : user.intervalid = setInterval(test, 1000, 'room', 20) Whereas in simple Javascript it returns a simple INTEGER number So, if you have some piece of long running node.js code, it will block all other events (including timer events) until it is done and node.js can get back to pulling the next event out of the event queue.This is my JS in nodeJS : function test(a, room, seconds) , Instead, node.js will wait until the current thread of execution in node.js is done and then, and only then, the next event in the event queue will be pulled out and the appropriate callback for that event will get called. If node.js is doing nothing at that moment, then the event is triggered immediately and the appropriate callback function is called immediately.īut, if node.js is busy running code and if other events are in front of the timer event in the event queue, then the timer event will not be triggered immediately. At that moment, an event is inserted into the node.js event queue. When you use setTimeout() or setInterval() some internal mechanism inside of node.js uses system timers to know when the next timer should fire. Learn how to use setTimeout and setInterval to schedule functions in the. Node.js is a single threaded event-driven system (technically threads are used inside of node.js, but it only runs one single thread of your JS code). When writing JavaScript code, you might want to delay the execution of a function. Here's some explanation of how the node.js system works. Yes, it waits until the current code executing in node.js is done before it can serve the next timer event. Set of long running commands, does Node.js/JavaScript wait until thoseĬommands finish executing the function set up in setTimeOut? If I call setTimeOut() for say, 10 seconds from now, then execute a Timer events in node.js are not guaranteed to be called at an accurate time.
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