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@naserca @func_i
Own Your Front-end Performance Tools, Not Rules
Alex Naser @naserca Laith Azer @func_i
devhub - devmonth April 14, 2016
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“Don’t Be Slow”
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@naserca @func_i
fast as possible response times measure via benchmark
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Rules!
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Hash#mergevs
Hash#merge!
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Hash#mergevs
Hash#merge!
24x slower
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Array#unshiftvs
Array#insert
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Array#unshiftvs
Array#insert
262x slower
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Easy!
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“Don’t Be Slow”
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@naserca @func_i
fast load, smooth animations measure
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fast load, smooth animations measure
how fast?
at what speed?
on what device(s)?
how fast?when?
images?
text?
how?
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Rules?!
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CSS animations vs
JS animations
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well…
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concat’d CSS files vs
separate CSS files
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well…
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Hard!
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“Don’t Be Slow”
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“Don’t Be Slow” “Don’t Feel Slow”
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Title slide
Subtitle Day Month, Year
users
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Title slide
Subtitle Day Month, Year
What are they doing?
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waiting for page to load tap nav icon watch animation of nav bar looking for link
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waiting for page to load
LOAD
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tap nav icon
RESPOND
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watch animation of nav bar
ANIMATION
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looking for link
IDLE
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RESPOND ANIMATION IDLE LOAD
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Paul Lewis Paul IrishTHANKS
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RESPOND tap or click < 100ms
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ANIMATION scroll or drag < 16ms (60fps)
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IDLE nada < 50ms
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LOAD first meaningful paint < 1s
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bad
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device
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network speed
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90th percentile
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websiteswebsites
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Google: 2% slower = 2% less searching per user Yahoo: 400 milliseconds faster = 9% more traffic Amazon: 100 milliseconds faster = 1% more revenue
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Rules?! Tools!
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1. html 2. ? 3. website
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1. html 2. critical rendering path 3. website
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1. DOM 2. CSSOM 3. render tree 4. layout (reflow) 5. paint
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1. DOM Document Object Model
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<html>
<head>
<meta name="viewport" content="width=device-width">
<link href="style.css" rel="stylesheet">
<title>Critical Path</title>
</head>
<body>
<p>Hello <span>web performance</span> students!</p>
<div><img src="awesome-photo.jpg"></div>
</body>
</html>
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2. CSSOM CSS Object Model
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body { font-size: 16px }
p { font-weight: bold }
span { color: red }
p span { display: none }
img { float: right }
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render blocking (by default)
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FOUC
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3. render tree
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4. layout (reflow)
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calculate exact position and size
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<html>
<head>
<meta name="viewport" content="width=device-width">
<title>Critical Path</title>
</head>
<body>
<div style="width: 50%">
<div style="width: 50%">Hello world!</div>
</div>
</body>
</html>
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style changes fetching of layout/scroll adding/removing els
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5. paint
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paint *itself* “composite layers”
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<html>z-index’d & positioned opacity < 1 overflow
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CPU & GPU
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void draw(SkCanvas* canvas) { canvas->drawColor(SK_ColorWHITE);
SkPaint paint; paint.setStyle(SkPaint::kFill_Style); paint.setAntiAlias(true); paint.setStrokeWidth(4); paint.setColor(0xffFE938C); SkRect rect = SkRect::MakeXYWH(10, 10, 100, 160); canvas->drawRect(rect, paint);
SkRRect oval; oval.setOval(rect); oval.offset(40, 80); paint.setColor(0xffE6B89C); canvas->drawRRect(oval, paint);
paint.setColor(0xff9CAFB7); canvas->drawCircle(180, 50, 25, paint);
rect.offset(80, 50); paint.setColor(0xff4281A4); paint.setStyle(SkPaint::kStroke_Style); canvas->drawRoundRect(rect, 10, 10, paint);}
@naserca @func_i
1. DOM 2. CSSOM 3. render tree 4. layout (reflow) 5. paint
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javascript
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synchronous DOM blocking
(by default) (scary)
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requires CSSOM
@func_i @naserca functionalimperative.com
But wait, there’s more!
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ANIMATION scroll or drag < 16ms (60fps)
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60Hz
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1000/60 = 16.67ms per frame
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JavaScript Animations
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function draw() { // Drawing code goes here}setInterval(draw, 1000/60);
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∞
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YOLO
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juggling
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requestAnimationFrame🙌
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function draw() { requestAnimationFrame(draw); // Drawing code goes here}draw();
function draw() { // Drawing code goes here}setInterval(draw, 1000/60);
@func_i @naserca functionalimperative.com
Go get ‘em!
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