jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

Avaq

const I  = x => x
const K  = x => y => x
const A  = f => x => f (x)
const T  = x => f => f (x)
const W  = f => x => f (x) (x)
const C  = f => y => x => f (x) (y)
const B  = f => g => x => f (g (x))
const S  = f => g => x => f (x) (g (x))
const S_ = f => g => x => f (g (x)) (x)
const S2 = f => g => h => x => f (g (x)) (h (x))

YusukeHosonuma

-- | recursion version

map' :: (a -> b) -> [a] -> [b]
map' _ [] = []
map' f (x:xs) = f x : map' f xs

filter' :: (a -> Bool) -> [a] -> [a]
filter' _ [] = []
filter' f (x:xs)
  | f x       = x : (filter' f xs)

Avaq

Ramda	Sanctuary
add(a, b)	add(b, a)
addIndex(f)	``
adjust(f, i, xs)	``
all(f, xs)	``
allPass(fs, x)	allPass(fs, x)
always(x)	K(x)
and(a, b)	and(a, b)
any(f, x)	``

jaysonsantos

extern crate ring;

use ring::aead::*;
use ring::pbkdf2::*;
use ring::rand::SystemRandom;

fn main() {
    // The password will be used to generate a key
    let password = b"nice password";

JoelQ

-- 0.19

randomToTask : Generator a -> Task x a
randomToTask generator =
    Time.now
        |> Task.map (Tuple.first << Random.step generator << Random.initialSeed << Time.posixToMillis)


-- 0.18

gaearon

Note:

When this guide is more complete, the plan is to move it into Prepack documentation.
For now I put it out as a gist to gather initial feedback.

A Gentle Introduction to Prepack (Part 1)

If you're building JavaScript apps, you might already be familiar with some tools that compile JavaScript code to equivalent JavaScript code:

• Babel lets you use newer JavaScript language features, and outputs equivalent code that targets older JavaScript engines.

nicolasdao

Install

npm install -D acorn babel-loader @babel/core @babel/preset-env babel-polyfill webpack webpack-cli uglifyjs-webpack-plugin --save-dev

webpack-cli and acorn are dependencies that you, unfortunately, have to install if you want to run this god damn thing without any obscure warnings or errors.

Build

Configure Webpack

pinkhominid

const fs = require('fs');
const fetch = require('node-fetch');
const FormData = require('form-data');

const filePath = `path/to/file.ext`;
const form = new FormData();
const stats = fs.statSync(filePath);
const fileSizeInBytes = stats.size;
const fileStream = fs.createReadStream(filePath);
form.append('field-name', fileStream, { knownLength: fileSizeInBytes });