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ImageMagick commands

Image information

identify <image>

Resize an image

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// if our data is more complicated and has to form things from items for example
// just pass around list of functions
const API = {
  github: (username) => 'http://github.com/' + username,
  photo: (username) => `http://github.com/${username}/avatar/`
}
const users = ['bahmutov', 'adity']
Object.keys(API).forEach((apiName) => {
  const formApiUrl = API[apiName]
  describe('api ' + apiName, () => {

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// A: is this pure function?
function sum(a, b) { return a + b }
// B: is this a pure function?
const k = 2
function addK(a) { return a + k }
// C: is this a pure function?
function sub(a, b) { return sum(a, -b) }
// D: is this a pure function?
function sub(a, b, summer) { return summer(a, b) }
// E: is this a pure function?

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Goal: run a simple NodeJS application inside a Docker container

Subgoal: give it access to local files.

docker run -it --rm --name example -v "$PWD":/usr/src/app -w /usr/src/app node:5-slim node index.js

output:

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On Mac OSX

To find the local network (WIFI usually) address ipconfig getifaddr en0

ipconfig getifaddr en0

192.168.0.8

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Goal: try redis inside a Docker container

Run Redis Docker image

1. Open docker terminal

• displays docker is configured to use the default machine with IP 192.168.99.100

2. Start redis:alpine prebuilt container from docker hub.

• docker run --name redis -p 6379:6379 -d redis:alpine
• the "alpine" image is very slim (5MB!)
• the running container binds the internal port 6379 to the "outside" world port with same number

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# See list of docker virtual machines on the local box
$ docker-machine ls
NAME      ACTIVE   URL          STATE     URL                         SWARM   DOCKER   ERRORS
default   *        virtualbox   Running   tcp://192.168.99.100:2376           v1.9.1 

# Note the host URL 192.168.99.100 - it will be used later!

# Build an image from current folder under given image name
$ docker build -t gleb/demo-app .

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// node-canvas
var Canvas = require('canvas')
console.log('Canvas is', Canvas)
var nodeCanvas = new Canvas(120, 120)
var ctx = nodeCanvas.getContext('2d')

// canvas-5-polyfill patches CanvasRenderingContext2D.prototype
// lets give it one
global.CanvasRenderingContext2D = {};
global.CanvasRenderingContext2D.prototype = ctx;

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Setting up Git message validation hook

Install pre-git for handling Git hooks and commitizen for helping format the commit messages

npm install pre-git commitizen cz-conventional-changelog --save-dev

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// NOTE does not work in strict mode
function parent(a, b) {
  console.log('in parent, a', a, 'b', b);
  var parentArguments = arguments;

  function child() {
    console.log('in child, a', a, 'b', b);
    console.log('is parentArguments === c.args?', parentArguments === c.args);
    console.log('parentArguments', parentArguments);
    return a + b;