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Asynchronous Programming with JavaScript

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Introduction to Asynchronous JavaScript

2:45 with Guil Hernandez

Any time you have code that needs to execute after some period of time, in response to an event (like a mouse click), or upon receiving the data it needs, you're introducing asynchronous behavior into your program. JavaScript and its runtime environment provide efficient ways to handle async operations.

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    [MUSIC] 0:00
    Most applications interact with the outside world and often need to handle and 0:08
    process multiple things at a time. 0:12
    For example, accept user input, request data from the server, or 0:14
    send data across the network and wait for a response. 0:18
    Some apps might perform repeated task at a fixed interval of time, 0:21
    like display a timer that updates the UI every second. 0:25
    If you've written a fair amount of JavaScript, there's a good chance that at 0:28
    some point you've written code to handle these types of tasks. 0:32
    JavaScript is a synchronous single threaded language, 0:36
    which means that it can process and execute only one task at a time. 0:39
    Some tasks take time to execute. 0:43
    If there's a major delay between the start and end of an operation and 0:45
    nothing else can run during that time, it's going to create issues in your app, 0:49
    which negatively affect performance and the overall user experience. 0:52
    For instance, a function that's stuck waiting for data 0:56
    requested from a server can make an app feel completely frozen and unresponsive. 0:59
    The user will not be able to do anything until the requested data 1:04
    is eventually returned. 1:07
    Any time you have code that needs to execute after some period of time in 1:09
    response to an event, like a mouse click, or upon receiving the data it needs, 1:13
    you're introducing asynchronous behavior into your program. 1:17
    JavaScript and 1:21
    its runtime environment provide efficient ways to handle async operations. 1:22
    I'm Guil, a developer and JavaScript instructor here at Treehouse. 1:27
    In this course, I'll introduce you to the ways JavaScript makes it possible to 1:30
    program in an asynchronous way, that is allow other parts of your program to 1:33
    carry on and run while other potentially blocking script wait to complete. 1:38
    If you're used to programming JavaScript in a synchronous style where one statement 1:43
    needs to run and execute before the next statement does, it might be challenging to 1:47
    wrap your head around the concepts of asynchronous programming at first. 1:51
    So in this course you'll first learn the differences between synchronous and 1:55
    asynchronous code and go over examples of each using JavaScript. 1:59
    You'll get an introduction to the mechanics of asynchronous programming in 2:03
    the browser, learning concepts like JavaScript's call stack and event loop. 2:07
    You'll get to know why asynchronous code matters and how to design code that 2:11
    avoids blocking behavior using common async patterns like callback functions and 2:15
    promises to the modern async await pattern. 2:20
    By the end, you'll have learned to write asynchronous programs that 2:23
    result in cleaner, more performant code. 2:26
    Now this course assumes that you have experience working with JavaScript and 2:29
    the DOM as well as understand the basics of sending HTTP requests and 2:32
    receiving responses. 2:36
    You should also feel comfortable with using callback functions. 2:38
    If not, be sure to review the resources posted in the teacher's notes first 2:41
    to get up to speed. 2:44

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