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Modified Preorder Tree Traversal

Hierarchical data metrics that allows fast read operations on tree like structures.

Based on Left and Right fields that are set during tree traversal. When entered into node value is set to it's Left, when exiting node value is set to it's Right.

Sample implementation

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--select ARRAY(select distinct unnest(array_agg(category.arr)))
select ARRAY(select distinct unnest(array[array[1,2,3], array[4,2,8]]))

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Resolving missing link to libcrypto openssl on OSX from: http://stackoverflow.com/questions/38670295/brew-refusing-to-link-openssl

brew update

brew install openssl

ln -s /usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib /usr/local/lib/

ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/

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#!/bin/bash
# node-reinstall
# credit: http://stackoverflow.com/a/11178106/2083544

## program version
VERSION="0.0.13"

## path prefix
PREFIX="${PREFIX:-/usr/local}"

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const { rxObserver, palette } = require('api/v0.3');
const { merge, timer, Subject, from, empty } = require('rxjs');
const { filter, startWith, bufferToggle, take, flatMap, zip, distinctUntilChanged, share, skip, map, windowToggle } = require('rxjs/operators');

// stream for coloring
const palette$ = from(palette);

const source$ = timer(0, 10).pipe(
    take(10),
    // get color for each item

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Libraries and Tools for React

Components and Component Libraries

If you're developing an application based on React it can be helpful if you don't need to develop all the basic UI components yourself. Here you can find a list with various components, component libraries and complete design systems developed with and for React.

Component libraries and Design Systems

Brands (official design systems by various companies and products)

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// Add a 401 response interceptor
window.axios.interceptors.response.use(function (response) {
    return response;
}, function (error) {
    if (401 === error.response.status) {
        swal({
            title: "Session Expired",
            text: "Your session has expired. Would you like to be redirected to the login page?",
            type: "warning",
            showCancelButton: true,

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// based on Алексей Сердюков's answer at Stackoverflow (https://stackoverflow.com/a/50837219/1143392)

import {
  Directive,
  Input,
  OnDestroy,
  OnInit
} from '@angular/core';
import { MediaObserver } from '@angular/flex-layout';
import { MatGridList } from '@angular/material';

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Git Submodules basic explanation

Why submodules?

In Git you can add a submodule to a repository. This is basically a repository embedded in your main repository. This can be very useful. A couple of advantages of using submodules:

• You can separate the code into different repositories.

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Git

Global Settings

• Related Setup: https://gist.github.com/hofmannsven/6814278
• Related Pro Tips: https://ochronus.com/git-tips-from-the-trenches/
• Interactive Beginners Tutorial: http://try.github.io/
• Git Cheatsheet by GitHub: https://services.github.com/on-demand/downloads/github-git-cheat-sheet/

Reminder

Press minus + shift + s and return to chop/fold long lines!