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🏋 "RAIL", Important way of thinking about frontend performance

😎 Don't guess, measure !

❌ This is the reason why this website is slow !! I know it!
✅ Well... I'm gonna just measure, drinking coffee

But after measuring performance, maybe you would think like that

😑 Hey, I measured... but I don't have goal! 1second? 2second? What is criterion??

😎 Ok I give you basic performance criterion, tadaaam RAIL
😑 Ruby on rails?
😎 No, there is no relationship with it at all, RAIL is based "Response, Animation, Idle, Load"

Content criterion time
Response 100ms
Animation 16ms
Idle 50ms
Load 1000ms

⭐ Response

some action should response less than 100ms, after user inputs something

Click! ----- less than 100ms -----> open modal
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⭐ Animation

Animation(video) is just collection of a lot of images actually. So it's important to know how many images there is in "A second"
Referenece video

content number of images in a second
TV 30
Movie 24
Game 60
PC 60

Now Let's do super easy math

1s - 60images
16ms - 1image
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This is the reason why animation should finish less than 16ms

By the way this unit of How many images there is in a second is called FPS(Frames per seconds), so animation on PC is 60fps

▼ for example, configuration of chartjs-plugin-streaming, there is "frameRate"

⭐ Idle

After loading contents, looks like browser doesn't do anything, but still do something like getting data from API by XHR or lazy load images. These actions should be less than 50ms

😀 click Url!
😀 finish rendering and we see something on browser!
😭 wait, Im browser, I need to load images that I didn't on purpose at first
↓ (50ms)
😭 Ok I've done it! I don't use main thread finally!
😀 ohh I can handle now on browser now!!
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⭐ Load

loading time of webpage contents

I wanna see! click url!
↓ (1 second)
I see contents on browser and handle something as well!
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actually it's not necessary to load all contents at first.
Important thing is that loading contents in which user see on browser.

first view

→ Next article "then how to measure them??"

Top comments (2)

svgatorapp profile image

Really enjoyed reading this series!

kaziusan profile image

Thank you very much :)
Actually I will be engaged in real project "Improve Page Speed Insights score and whole frontend", so I hope I will share about it someday 😎