My goodness. First you need a way of making HTTP calls from your program to websites. function underrun_callback(queue: GstElement * queue, udata: gpointer udata): { // javascript callback for the 'underrun' signal } Reports that the buffer became empty (underrun). [00:04:58] It's called, it's a queue. Consider an E-Commerce app, where users can do everything except checkout without being logged in. That is, the JavaScript engine can only process one statement at a time in a single thread. Is there anything in the queue? But it's more than that.

The second() function finishes, so it’s popped off the stack. Hence, the program is finally terminated. In the future this will throw an exception! When you need to do heavy computation, which is not required to run sequentially, means next statement can be executed without it. Heap is used to allocate memory and stack to do the function calling. You are going to use three endpoints of this API: /directors returns list of movie directors. [00:12:30] Is there anything on the call stack? Yeah, Kayla.>> off screen female: The global execution context has to be done.

That is, the event loop will first empty the micro-task queue before executing any callback in the message queue.

The Message queue also contains the callbacks from the DOM events such as click events and keyboard events. The call stack becomes empty only at 1002 ms when the block1Second function has finished executing and is removed from the call stack. [LAUGH]>> [LAUGH]>> Will Sentance: Instead, our poor little printHello is gonna sit there and what's gonna run instead, Todd?>> off screen male: The console.log me first.>> Will Sentance: console.log me first, exactly right. At this point, the callback has finished so it’s removed from the stack and the program finally finishes. I’d be happy to help :), document.querySelector('.btn').addEventListener('click',(event) => {, 7 Top React Static Site Generators in 2020, Web Component: Why You Should Stick to React, 6 Reasons to Use React Hooks Instead of Classes, React Query — An Underrated State Management Tool. At last when the networkRequest() function completes, greeting() function is called and since it contains only a console.log statement and console.log statements are generally fast, so the greeting() function is immediately executed and returned. As we have seen before, the setTimeout function was scheduled to be executed at a timestamp of 1001 ms. This enables websites to run JavaScript in client browsers and standalone JavaScript applications to run in Node.js. /directors/{id}/movies returns a list of movies made by the specified director. Begin your exploration of concurrency in JavaScript by initializing a new Node.js project. After that the console.log(‘Async Code’) is pushed to the top of the stack, executed and popped off from the stack. So my event loop throughout goes, is the call stack empty at blockFor1Sec, everybody? So, here comes the async nature of Javascript. And we're going to invite Ethan, no, no, no [LAUGH] Ethan's line was excellent. Instead, it's just grabbing that function, [SOUND], throwing it out here. The setTimeout() has two arguments: 1) callback and 2) time in milliseconds (ms). At 1,001 milliseconds, is there further global code still to run?>> off screen male: Yes.>> Will Sentance: Yeah, so the event loop goes, no, you can't.

In the post 5 Ways to Make HTTP Requests in Node.js you can find a comparison of some popular libraries used to perform HTTP requests in Node.js. Let’s get back to the above code snippet and try to understand how the code executes inside the JavaScript engine. So, in our case, the function is to be executed only at a timestamp of (1 + 1000) = 1001 ms. What do we want to have happen?>> off screen male: You want it to run the printHello.>> Will Sentance: Perfect, run the printHello function. Let us assume that it contains some code that takes approximately 1 second to run, for e.g. All global coast finish running, and we grab from the Callback Queue and put printHello in the Call Stack. This is a callback function: it's a function you want to run after the function to which you're passing it as an argument does whatever it's supposed to do. Is that kinda,>> Will Sentance: Is it complete? We're not writing its code out, but if we ran it, you would run some sort of for loop, or something like that. No, finally I get to go down.

When the event loop gets fired, it sees that the call stack is non-empty. We're going to call this setTimeout. We shall learn about it in the final part of this series. Example code: setTimeout takes a callback function as first parameter, and time in millisecond as second parameter.