All right, let's kick things off today. We're going deep on ACYNK JavaScript and how to write code that's not just functional but really sings performance wise.
Yeah, we're talking speed exactly.
And to guide us on this journey, we have Kyle Simpson's book You Don't Know JS, A sink and Performance.
It's a fantastic resource, really digs deep.
I've got to say this book was a game changer for me.
Absolutely.
When I first started with ACYNK JavaScript, it felt like I don't know, my brain was doing backflips.
It's definitely a mind bender, especially that.
Whole concept of later. You know how JavaScript handles things that can't happen right away right right. It's not exactly intuitive.
It's like we assume later means well right.
After now, Yeah, like step one, step two.
But in javascripts later it's a whole different beast.
So let's say you're making an ajax call to grab some data from a server. Okay, you write the code, you make the call, and then you try to log the data. You know, right after it seems logical, yeah, but then nothing.
It's like where the data go proof vanish. The trick is we're thinking in a straight line but when you're dealing with things like timers, clicks, those AgeX responses, we're in the land of a synchronicity.
Okay, so things are getting shuffled around exactly.
Things don't always happen in a predictable order.
So how does JavaScript decide what happens now versus what gets pushed to this mysterious later.
It all comes down to this thing called the event loop.
Okay, the event loop.
Think of it like a queue, a never ending queue of.
Tasks, all right. So each task gets.
Its turn exactly, Each task gets its moment to run, and then boom, event loop moves on to the next one.
It's like a very organized but super fast game of musical chairs.
You got it.
But what about set time out?
Ah?
Set time out is just like chuck the function into queue immediately.
Not quite. It's more like it sets a timer okay, and when the timer goes off, it's like the function taps the event loop on the shoulder and says, hey, I'm ready now.
Ah. It's like a reservation system for our code.
I like that, a reservation system.
But this brings up something that's always tripped me up. What's concurrency? Ah? Concurrency what happens when multiple things are trying to happen at the same time.
It's a great question and important to remember. Even though JavaScript doesn't have traditional threads, we still have to deal with concurrency because at its heart it's single threaded.
So it's like having one chef trying to cook multiple dishes at once.
Exactly. They can only work on one thing at a time, but they've got to keep switching back and forth.
So how do we make sure we're not creating kitchen chaos in our code? Right?
We don't want everything burning?
What happens when multiple functions try to access and you know, change the same data at the same time.
It can get messy. But one way to manage this is using something called mutual exclusion.
Mutual exclusion okay, like.
Putting a lock on a shared resource.
So only one function can access it at a time.
You got it. You can think of it like a simple if statement that checks if a variable is being used.
So it's like those occupied signs on a restroom stall.
Perfect analogy.
It's got a wait, it's turned exactly now, what about breaking down those tasks into smaller chunks?
Ah, you're talking about cooperative concurrency.
That's it.
It's all about sharing the stage.
So instead of one function hogging the event loop for ages, we break.
It down right into smaller steps, give other functions a chance to run, so.
We avoid that event loop traffic jam exactly. Okay. I gotta be honest, though, the fact that JavaScript can actually re order statements in my code, that kind of freaks me out.
I get it. It feels like our code is being rearranged behind our backs, right, But remember the JavaScript engine, it's smart, okay. It's always looking for ways to optimize our code, and sometimes that means rearranging things as long as the final result is the same.
So it's like having a super efficient editor.
Exactly.
They clean up our writing, but the meaning stays the same precisely. That makes me feel a bit better.
Good, good, But it still.
Makes it hard to picture, you know, what happens when, especially with all these asynchronous events flying around.
It's true we're wired for linear thinking, but asynchronous code it's much more fluid. Ye think about trying to run errands and take phone calls at the same time. Oh yeah, You start one task, get interrupted by a call, go back to the task, interrupted again.
It's impossible to plan everything perfectly in a straight line, exactly.
You can't predict when those calls are going to come in.
And I feel like that chaotic feeling gets amplified when we start using nested callbacks.
Oh, nested callbacks they can get out of hand.
It's like following a recipe where every step sends you on a wild goose chase for another ingredient.
Right, You're jumping all over the place.
And then you end up with a kitchen that looks like a tornado hit.
It, exactly. And nested callbacks they can turn into a tangled mess.
They make our code harder to understand, harder to debug, harder to maintain. Absolutely, which brings us to the well, the darker side of callbacks. Ooh, what's that the trust issues?
Trust issues with a our own code.
Yeah, shouldn't we be able to trust ourselves ideally?
Yes, but remember in this acinc world, things get unpredictable. Even our own code can behave in ways we don't expect, especially when we're dealing with external libraries.
Okay, you're losing me a little.
Okay, imagine this. Yeah, you're adding a third party analytics tool to your website. You know, for tracking purchases. Okay, yeah, you hand over your purchase data to their library. Everything seems to be working fine. You pat yourself on the back. Job, well done, right, good job. Months later, your boss calls panicked. Oh no, a customer was charged five times for the same item.
Oh that's a nightmare.
It is. And after some frantic debugging, you find out that the analytics library was silently retrying the purchase callback multiple times, leading to those duplicate charges.
It's like handing over the keys to your car and hoping they won't go on a joy ride.
That's exactly the problem with callbacks, this inversion of control.
We're handing over control and just hoping for the best.
Right, But there's a better way.
Tell me, there's a better way. Promises promises, those sound promising, They tell me more.
A promise is essentially a contract for a future.
Value, so like a guarantee in a way.
Yeah, it's like saying, I promise to get back to you with the result of this operation.
Whether it's a success or a failure.
Exactly.
So, instead of relying on this potentially flaky callback, we have a more structured approach.
It's more reliable. I like it, and with promises, we keep control over the flow of execution.
Okay, so we get to decide what happens next exactly.
We define what should happen when the promise is fulfilled meaning the operation was successful, or rejected meaning there was an error.
Okay, promises sound like a much safer bet they are. Could you walk me through an example. Maybe you know with our trustee ajax call.
Absolutely, So instead of passing a callback function to that ajax call, we create a promise that represents the result of the request Okay, and then, using the then method, we specify what should happen when the promise resolves successfully.
So it's like, if this happens, then do this you got it?
And if something goes wrong, we can use the catch method to handle the error gracefully prevents our app from crashing.
Okay. So promises make our asynchronous code more robust and predictable exactly. But what about when we have multiple asynchronous operations we need to do in sequence.
Ah, That's where the magic of promise chaining comes in.
Okay, promise chaining, you can use the.
Then method to chain together a series of asynchronous steps.
Each one depending on the one before it exactly.
It's like a domino effect. Each step triggers the next.
Okay, so instead of juggling all these promises at once, we create this smooth, organized flow precisely.
It's all about creating a clear sequence of events.
I love it. But what about situations where we have multiple promises happening concurrently, Like let's say we need to fetch data from multiple URLs at the same time.
Ah, for that, we have promise at all at all. It's like waiting for all your friends to get ready before you head out for the night.
You pass it in an array of promises.
Yep, and it gives you back a new promise that resolves when all of those promises have resolved.
So it's like okay, everyone's here, let's go exactly.
And the best part is Promise all gathers all the results from those promises into a nice array, so you can work with the combined data easily.
Okay, So promises can handle these complex scenarios, both sequential and concurrent.
They're very versatile.
I'm impressed I did. But earlier we were talking about you know, those nested callback nightmares with event handlers. Oh yeah, can promises help us out there too.
They can, but we got to be careful. Okay, if we're not careful, we might just be trading one type of complexity for another.
Okay.
Creating a new promise chain inside each event handler can get.
Messy, right, redundant code.
It makes things hard to manage.
So what's the secret to using promises effectively with event handlers.
It's about shifting our perspective. Instead of creating a promise chain within the event handler, we can use observables.
Observables. You mentioned those earlier. They sound pretty advanced.
They're powerful, but the core concept is actually quite simple. Okay, think of an observable like a stream of events, right, like a flow of data exactly. You can subscribe to an observable and react to each event that comes through that stream using you guessed it promises.
So it's like setting up a sensor. When it detects a change, it triggers a specific action.
Perfect analogy.
Okay, So observables sound like a whole other deep dive.
We could definitely spend a whole episode on those, but.
For now, let's move on to generators.
Generators another powerful tool in our acinc toolkit.
I gott admit I haven't quite wrapped my head around them yet.
They're a really cool way to write asynchronous code that looks and feels synchronous.
Wait, so you can write ACYNC code that looks like it's running in a stray line.
You got it. Generators let you pause and resume execution using the yield keyword, like.
Having a pause button for our code.
Exactly. You can pause the execution, wait for an asynchronous operation to complete, and then resume right where you left off.
Okay, my mind is blown. How does that even work?
Imagine you have a function that needs to fetch data from a server. With a generator, you can yield control at the point where the request is made.
Okay, Then when the data is available, you can resume the function right where you left off.
So it's like breaking down a long task into smaller, more manageable chunks exactly.
And the best part is the code inside the generator reads like a synchronous story.
Okay, this is starting to make sense. Good, good, But how do we actually use this with real world asynchronous operations.
That's where promises come back into play. Okay, we can create a promise that wraps the execution of the generator using yield to delegate to promises for asynchronous tasks.
So we get the best of both worlds exactly.
The synchronous looking code of generators combined with the trust and composability of promises.
Wow, that's powerful.
It is.
But what about those of us who are still supporting older browsers, you know, the ones that haven't quit caught up to the whole generator scene.
Don't worry, we got you covered.
Okay.
We can use a technique called transpiling, which basically translates our fancy ES six code, including generators, into code that older browsers can understand.
So it's like a universal translator for JavaScript exactly.
Okay, so we have options even when we're dealing with those legacy browsers.
Always good to have options.
I feel like we've covered so much ground already.
We have, but we're just getting started.
Oh man, my brain is already full.
It's a lot to take in. But it's exciting stuff.
It is exciting, and you know what, I'm ready to dive even deeper into the world of JavaScript performance.
Let's do it.
But first, a quick message from our sponsor, welcome back. Before the break, we were getting into generators and promises. How they can wrangle that asynchronous JavaScript all its quirks. Yeah, exactly. But there's another powerful tool we've got to talk about, and it's web workers. Ah.
Yes, web workers.
These things bring true parallelism to JavaScript.
They really do.
Imagine being able to run multiple pieces of code simultaneously, like having a whole team of chefs in the kitchen instead.
Of just won much more efficient.
Right, No more bottlenecks at the stove, exactly. But how do these webworkers actually work? Do they have their own like little JavaScript universe in a way.
Yeah, Each webworker runs in its own isolated environment, separate from the main thread.
So they're like independent apartments in a building.
That's a good way to put it.
They're separate, but can still, you know, communicate exactly.
They communicate through a system called message passing.
So it's like sending notes back and forth precisely.
They can request data, send results, coordinate their actions all without stepping on each other's toes.
Very civilized it is. But what about data structures? Can web workers access the same arrays and objects as the main thread?
Not directly, no, okay, But there's this clever mechanism called transferable.
Objects transferable objects.
It allows them to efficiently share data instead of copying, which can be slow. They transfer ownership, so.
It's like handing off a baton in a relay race.
Perfect analogy. Only one runner can hold the baton at a time, but they pass it on smoothly.
And that's way faster than making copies.
Much faster, especially when you're dealing with large amounts of data.
Okay, webworkers sound amazing, but are there any limitations?
Yeah? Well, every superhero has their kryptonite, right. Webworkers don't have direct access to the dom.
The dom, so they can't manipulate the user interface.
They're more like behind the scenes heroes, crunching numbers, processing data, but not messing with the visual stuff.
Got it. They're like the engine under the hood, not the flashy pain job exactly. But what about libraries in external code? Can they use those?
Absolutely? Webworkers can use a function called import scripts to load external JavaScript files. It's like giving them a whole toolbox.
So we could equip them for any task you got it. But what about older browsers, you know, the ones that haven't gotten the memo about web workers.
For those cases, we have polyphills polyphills. They can emulate the behavior of webworkers even in those older browsers.
It's like finding a vintage record player that can play modern digital music exactly.
You get the functionality, even if the browser doesn't natively support it.
That's awesome, it is. Okay, before we move on, I've heard this term thrown around SIMD. What is that all about?
SIMD stands for single instruction multiple data.
Okay, that sounds intense.
It's a way to perform the same operation on multiple pieces of data at the same time.
So it's like having an assembly line of robots, each one doing the same task but on a different item.
Perfect analogy. It's mass production for data processing, very efficient, incredibly efficient, especially for computations involving large data sets.
Okay, so we've got web workers for task parallelism, multiple workers tackling different tasks, right, and then sim and D for data parallel processing multiple pieces of data at once.
You got it. It's all about finding the right tool for the job, leveraging parallelism to boost performance.
This is blowing my mind. JavaScript can do so much these days.
It really can, and it's only getting more powerful.
So what's next on the horizon? For JavaScript performance.
Well, there are some exciting proposals for new features that could bring even more parallelism to JavaScript, potentially allowing for direct threaded functionality.
Wait direct threads in JavaScript.
That's the idea. It's still early days, but the possibilities are huge.
So we might be able to write truly parallel code without relying on web workers or SIMD.
That's the goal.
That would be a game changer.
It would revolutionize how we approach JavaScript performance.
This deep dive has been like a crash course in JavaScript optimization.
We've covered a lot of ground.
From the event loop, to concurrency, to web workers to SIMD. I feel like a JavaScript performance in ninja.
You're well on your way, But how do.
We actually know if our code is performing? Well? We can write all this async code, but how do we measure its efficiency?
That's where benchmarking comes in.
Benchmarking okay, it's the.
Process of systematically measuring the performance of your code, seeing how long it takes to execute certain operations. It's like taking your code for a test drive on a racetrack.
I love that analogy.
You see how fast it can go.
So how do we actually benchmark our JavaScript code? Do we need special equipment.
Not necessarily. For simple tests, you can use the built inconsole dot time and console dot time end methods.
Okay, so we can get a quick snapshot using the console exactly.
It's like using a stopwatch to time your code.
But I'm guessing there are more sophisticated tools out there for serious benchmarking.
Absolutely. If you need more detailed measurements, you can use libraries like benchmark dot js.
Benchmark dot js okay.
It allows you to run multiple tests, collect data, even calculate the margin of error.
Wow, margin of error. We're getting serious now.
It's all about getting and reliable data so you can make informed decisions.
So let's say we've run our benchmarks, we have some data. Now comes the fun part tuning. Where do we even begin.
The first step is to identify the bottlenecks, the parts of your code that are slowing things down.
So it's like finding the weak link in a chain.
Precisely. Once you've found the bottlenecks, you can start exploring different optimization strategies.
It's like being a code detective searching for clues to improve performance.
Exactly, And just like a good detective, you need the right tools and techniques.
So what are some common strategies for optimizing JavaScript code.
One common approach is to reduce the number of function calls.
Okay. Function calls can.
Be expensive, they can be, so minimizing their use can often lead to performance gains.
So it's all about streamlining the flow of execution.
Exactly, make it as smooth as possible.
What about object creation? I've heard that creating lots of objects can slow things down.
You're right. Object creation, especially for large or complex objects, can be a performance hit.
Okay, So minimize unnecessary object creation.
That's a good rule of thumb.
Got it. Reduce objects, streamline functions, check and check. But what about arrays? Any tips for optimizing code that works with a RaSE?
Absolutely? For example, when you're looping through an array, it's often more efficient to cache the length of the array rather than recalculating it on each iteration.
Ah. So it's like remembering how many ingredients you need instead of recounting them every time you add something to the bowl.
Exactly. It's a little shortcut for your code.
Very clever. I like it. Good, good, Okay. What about async specific optimizations? Any things to keep in mind when working with promises, generators, web workers definitely.
When working with promises, it's generally best to resolve or reject them as soon as possible. No need to.
Delay, okay, So keep those promises flowing exactly.
And with generators, remember that each yield represents a potential pause point. Use them strategically, like.
Hitting the pause button on a movie.
Right. You don't want to pause every few seconds, got it?
Use yield strategically and keep those promises moving precisely. But earlier, you mentioned that different JavaScript engines might optimize code in different ways.
That's true.
Does that mean we need to write code that's specifically tailored to each engine?
Ideally we want our code to perform well everywhere, But the reality is different engines have their own quirks.
It's like trying to write a song that sounds good on both a grand piano and a ukulele exactly.
So how do we strike that balance?
How do we write code that's universally optimized?
Start with general optimization principles that apply across all engines, and then if you have specific bottlenecks, you can use feature detection trure detection okay, to identify the current engine and apply targeted optimizations, so.
We're gathering intel on the environment before we deploy our code.
Exactly. It's all about being adaptable, understanding the nuances of different JavaScript environments.
Okay, that makes senseick, But there's one more optimization concept I want to talk about. What's that pail call optimization?
Ah y, Yes. TCO a powerful technique for improving the performance of recursive functions.
Cursive functions those are the ones that call themselves, right, that's right, But I've heard they can be dangerous because of stack overflow errors.
They can be If a recursive function calls itself too many times, it can fill up the call stack and crash the program. That sounds bad, it can be, But TCO prevents this by optimizing how recursive functions are executed.
So TCO is like a safety net for recursive functions.
You could say that in a nutshell, when a function call is in the tail position, meaning it's the last operation performed by the function, the engine can reuse the existing stack frame instead of creating a new one.
So it's like recycling those.
Stack frames exactly, saves memory and improves performance.
That's very clever. TCO sounds like a must have for any serious recursive function.
It is, and luckily ES six made TCO a requirement, so modern JavaScript engines should all support it.
That's great. News is okay. We've covered a ton of ground here benchmarking, tuning different JavaScript engines TCO. My head is spinning.
That's a lot to take in. But you're doing great.
I'm starting to feel like I can actually write JavaScript code that performs well.
You're well on your way. Remember, optimizing JavaScript performance is an ongoing journey. There's always more to learn and explore.
It's a marathon, not a sprint exactly. But before we get too carried away with all this performance talk, I want to shift gears a bit and talk about something equally important. Readability.
Ah. Yes, readability just as important as performance, because what.
Good is super fast code if no one can understand it?
Exactly? Writing readable code is crucial for collaboration, maintainability, and your own sanity.
I've definitely encountered some code that felt like deciphering ancient hieroglyphics.
We have all been there.
It's like, what was I thinking when I wrote this?
But writing readable code is not just about avoiding confusion. It's about creating code that's enjoyable to work with.
Okay, making the code a pleasure.
To read, exactly, code that's clear, concise, and expresses your intent in a way that others can easily understand.
So how do we actually achieve that? How do we write code that's both efficient and elegant? And we're back. We were just talking about how important it is to write readable code, code does not just functional, but actually enjoyable to.
Work with, right, Because we all want our code to be elegant, but let's face it, we also want to squeeze every ounce of performance out of our JavaScript.
Absolutely, we're all about speed. But how do we find that balance between writing beautiful code and making it lightning fast?
It's a constant juggling act, and I think sometimes we get caught up in what we call micro optimizations. You know, those tiny tweaks that promise a performance boost, but do they actually make a real difference.
Oh, I've definitely been down that rabbit hole before, like obsessing over whether to use plus plus A or A plus plus.
Yeah, we've all been there.
Did it really matter in the end?
Probably not. It's easy to get fixated on those benchmarks that focus on isolated operations. But those tiny differences they often become insignificant when you look at the whole picture of a complex application.
It's like rearranging the furniture in your house to save a few steps. Technically more efficient, but does it really change.
Your life exactly. Context is key. Optimize for clarity and maintainability first. Then if you have performance bottlenecks, you can look at those micro optimizations. Right, don't sweat the small stuff exactly, focus on the big picture.
But even when we are focused on those bigger optimizations, we have to remember that different JavaScript engines might optimize things differently.
That's true. The javascriptspec gives engines a lot of leeway in how they optimize code. It's like having different chefs using the same recipe but maybe adding their own personal flare.
So our code might perform differently depending on the engine it's running on, even if we follow the same best practices.
Yep, exactly. Some times what was considered an optimization, well it's not the best approach anymore.
You mean, like what worked yesterday doesn't necessarily work today.
Right. For example, years ago, using a ray dot joined to put strings together was generally faster than using the plus operator. Interesting, But then JavaScript engines evolved got smarter. They did, and they introduced optimizations for the plus operator, and it became more efficient. So the landscape shifted.
So what's the takeaway here?
Be adaptable, stay informed about what's going on with JavaScript engines. What's best practiced today might not be tomorrow.
Got to stay ahead of the curve exactly.
But there's another interesting thing about these engines.
Oh, what's that.
They don't always execute code in the exact order it's written.
Wait, hold on, they could just rearrange my code.
Well, not rearrange randomly, but optimize. Okay, the engine can analyze your code figure out if reordering some statements would improve performance without changing the outcome, like a super efficient editor.
So they're making my code better without messing with the meaning exactly. Okay, I can live with that. Good. So we need to like trust the engine, but also be aware of this reordering thing exactly.
Now, speaking of optimization, there's one more concept I want to bring up, tail call optimization.
Tail call optimization or TCO as.
The cool kids call it, right, it can dramatically improve the performance of recursive functions.
Okay, remind me recursive functions those are the ones that call themselves.
That's right, but they can be tricky because of those pesky stack overflow errors.
Yeah, those can be a real headache. So TCO helps prevent those exactly.
With TCO, when a function call is in the tail position, meaning it's the very last thing the function does, the engine can optimize how it runs.
So instead of creating a brand new stack frame every time the function calls itself, it reuses the existing.
One precisely like recycling.
Very efficient, very clever. So TCO definitely something to keep in mind when working with recursive functions.
It is, and luckily modern jobscript engines all support it.
Well, that's a relief, it is. It feels like we've covered a whole universe of JavaScript performance in this deep dive. From the event loop and concurrency to promises and generators, web workers, benchmarking, tuning, and now TCO.
We've been on quite a journey.
My brain is overflowing, but in a good way.
It's a lot to absorb, but the key is to remember that this is just the beginning, right.
There's always more to learn and explore in the world's of javascripts.
Exactly, keep experimenting, keep pushing those boundaries and most importantly, have fun with it.
Couldn't have set it better myself, so to our listeners, thanks for joining us on this deep dive. Keep learning, keep coding, and keep that JavaScript running smooth and fast.