hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

O-Zone

(function (window) {
  var transitions = {
    'transition': 'transitionend',
    'WebkitTransition': 'webkitTransitionEnd',
    'MozTransition': 'transitionend',
    'OTransition': 'otransitionend'
  },
  elem = document.createElement('div');
 
  for(var t in transitions){

joeybaker

# print all the titles in the db
strings -a -t x id_stor  | pcregrep -M '[a-z0-9]{1,9}\stitles\[\n[a-z0-9]{1,9}\s(.*?)u$' | grep -v 'titles' | cut -d " " -f 2- | sort | uniq | sed 's/u$//' | sed 's/://' | sed 's/\///' > couchpotato_export.txt

# get all current movies
# note: with GNU sed, the `sed -E` should be `sed -r`
ls /Volumes/raid6/Movies | sed 's/ ([0-9][0-9][0-9][0-9])//' | sed -E 's/(.*), The/The \1/' | sort > movie_files.txt

# get the wanted movies
grep -v -f couchpotato_export.txt movie_files.txt

paulirish

Screencapture and animated gifs

I say "animated gif" but in reality I think it's irresponsible to be serving "real" GIF files to people now. You should be serving gfy's, gifv's, webm, mp4s, whatever. They're a fraction of the filesize making it easier for you to deliver high fidelity, full color animation very quickly, especially on bad mobile connections. (But I suppose if you're just doing this for small audiences (like bug reporting), then LICEcap is a good solution).

Capturing (Easy)

1. Launch quicktime player
2. do Screen recording

sorenlouv

function mySlowFunction(baseNumber) {
	console.time('mySlowFunction');
	let result = 0;	
	for (var i = Math.pow(baseNumber, 7); i >= 0; i--) {		
		result += Math.atan(i) * Math.tan(i);
	};
	console.timeEnd('mySlowFunction');
}

mySlowFunction(8); // higher number => more iterations => slower

radum

Charles Proxy Map Remote over HTTP or HTTPS

The Map Remote tool changes the request location, per the configured mappings, so that the response is transparently served from the new location as if that was the original request.

HTTP

Using this feature for http resources does't require anything else apart from just configuring your Map Remote entry.

Always make sure you are clearing your cache before you test. Even if Charles is configured properly you might not see the changes unless the browser gets the resource again from the server and not for its local cache.

gajus

The issue:

..mobile browsers will wait approximately 300ms from the time that you tap the button to fire the click event. The reason for this is that the browser is waiting to see if you are actually performing a double tap.

(from a new defunct https://developers.google.com/mobile/articles/fast_buttons article)

touch-action CSS property can be used to disable this behaviour.

touch-action: manipulation The user agent may consider touches that begin on the element only for the purposes of scrolling and continuous zooming. Any additional behaviors supported by auto are out of scope for this specification.

wesbos

#!/bin/bash
files=$(git diff --cached --name-only | grep '\.jsx\?$')

# Prevent ESLint help message if no files matched
if [[ $files = "" ]] ; then
  exit 0
fi

failed=0
for file in ${files}; do

marcysutton

NOTE: This is no longer an experiment! You can use the accessibility inspector in Chrome Devtools now, including a fantastic color contrast inspection tool. Read more: https://developers.google.com/web/updates/2018/01/devtools#a11y

---

Just like any good element inspector helps you debug styles, accessibility inspection in the browser can help you debug HTML and ARIA exposed for assistive technologies such as screen readers. There's a similar tool in Safari (and reportedly one in Edge) but I like the Chrome one best.

As an internal Chrome experiment, this tool differs from the Accessibility Developer Tools extension in that it has privileged Accessibility API access and reports more information as a result. You can still use the audit feature in the Chrome Accessibility Developer Tools, or you could use the aXe Chrome extension. :)

To enable the accessibility inspector in Chrome stable:

Rich-Harris

Stuff I wish I'd known sooner about service workers

I recently had several days of extremely frustrating experiences with service workers. Here are a few things I've since learned which would have made my life much easier but which isn't particularly obvious from most of the blog posts and videos I've seen.

I'll add to this list over time – suggested additions welcome in the comments or via twitter.com/rich_harris.

Use Canary for development instead of Chrome stable

Chrome 51 has some pretty wild behaviour related to console.log in service workers. Canary doesn't, and it has a load of really good service worker related stuff in devtools.