React Query Builder with Cube.js

React Query Builder with Cube.js

React Query Builder with Cube.js

Starting from version 0.4, the React Cube.js client comes with the <QueryBuilder /> component. It is designed to help developers build interactive analytics query builders. The <QueryBuilder /> abstracts state management and API calls to Cube.js Backend. It uses render propand doesn’t render anything itself, but calls the render function instead. This way it gives maximum flexibility to building a custom-tailored UI with a minimal API.

The example below shows the <QueryBuilder /> component in action with Ant Design UI framework elements.

The above example is from Cube.js Playground. You can check its source code on Github.

This tutorial walks through building the much simpler version of the query builder. But it covers all the basics you need to build one of your own.

Setup a Demo Backend

If you already have Cube.js Backend up and running you can skip this step

First, let’s install Cube.js CLI and create a new application with a Postgres database.

$ npm install -g cubejs-cli
$ cubejs create -d postgres react-query-builder

We host a dump with sample data for tutorials. It is a simple “E-commerce database” with orders, products, product categories, and users tables.

$ curl http://cube.dev/downloads/ecom-dump.sql > ecom-dump.sql
$ createdb ecom
$ psql --dbname ecom -f ecom-dump.sql

Once you have data in your database, change the content of the .envfile inside your Cube.js directory to the following. It sets the credentials to access the database, as well as a secret to generate auth tokens.

CUBEJS_DB_NAME=ecom
CUBEJS_DB_TYPE=postgres
CUBEJS_API_SECRET=SECRET

Now that we have everything configured, the last step is to generate a Cube.js schema based on some of our tables and start the dev server.

$ cubejs generate -t line_items
$ yarn dev

If you open http://localhost:4000 in your browser you will access Cube.js Playground. It is a development environment, which generates the Cube.js schema, creates scaffolding for charts, and more. It has its own query builder, which lets you generate charts with different charting libraries.

Now, let’s move on to building our own query building.

Building a Query Builder

The <QueryBuilder /> component uses the render props technique. It acts as a data provider by managing the state and API layer, and calls render props to let developers implement their render logic.

Besides render, the only required prop is cubejsApi. It expects an instance of your cube.js API client returned by the cubejs method.

Here you can find a detailed reference of the [<QueryBuilder />](https://cube.dev/docs/@cubejs-client-react#query-builder "<QueryBuilder />")component.

import cubejs from "@cubejs-client/core";
import { QueryBuilder } from "@cubejs-client/react";
const cubejsApi = cubejs("CUBEJS_TOKEN", { apiurl: "CUBEJS_BACKEND_URL" });

export default () => (
  <QueryBuilder
    cubejsApi={cubejsApi}
    render={queryBuilder => {
      // Render whatever you want based on the state of queryBuilder
    }}
  />
);

The properties of queryBuilder can be split into categories based on what element they are referred to. To render and update measures, you need to use measuresavailableMeasures, and updateMeasures.

measures is an array of already selected measures. It is usually empty in the beginning (unless you passed a default query prop). availableMeasures is an array of all measures loaded via API from your Cube.js data schema. Both measures and availableMeasures are arrays of objects with nametitleshortTitle, and type keys. name is used as an ID. title could be used as a human-readable name, and shortTitle is only the measure’s title without the Cube’s title.

// `measures` and `availableMeasures` are arrays with the following structure
[
  { name: "Orders.count", title: "Orders Count", shortTitle: "Count", type: "number" },
  { name: "Orders.number", title: "Orders Number", shortTitle: "Number", type: "number" }
]

updateMeasures is an object with three functions: addremove, and update. It is used to control the state of the query builder related to measures.

Now, using these properties, we can render a UI to manage measures and render a simple line chart, which will dynamically change the content based on the state of the query builder.

import React from "react";
import ReactDOM from "react-dom";
import { Layout, Divider, Empty, Select } from "antd";
import { QueryBuilder } from "@cubejs-client/react";
import cubejs from "@cubejs-client/core";
import "antd/dist/antd.css";

import ChartRenderer from "./ChartRenderer";

const cubejsApi = cubejs(
"YOUR-CUBEJS-API-TOKEN",
 { apiUrl: "http://localhost:4000/cubejs-api/v1" }
);

const App = () => (
 <QueryBuilder
   query={{
     timeDimensions: [
       {
         dimension: "LineItems.createdAt",
         granularity: "month"
       }
     ]
   }}
   cubejsApi={cubejsApi}
   render={({ resultSet, measures, availableMeasures, updateMeasures }) => (
     <Layout.Content style={{ padding: "20px" }}>
       <Select
         mode="multiple"
         style={{ width: "100%" }}
         placeholder="Please select"
         onSelect={measure => updateMeasures.add(measure)}
         onDeselect={measure => updateMeasures.remove(measure)}
       >
         {availableMeasures.map(measure => (
           <Select.Option key={measure.name} value={measure}>
             {measure.title}
           </Select.Option>
         ))}
       </Select>
       <Divider />
       {measures.length > 0 ? (
         <ChartRenderer resultSet={resultSet} />
       ) : (
         <Empty description="Select measure or dimension to get started" />
       )}
     </Layout.Content>
   )}
 />
);

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

The code above is enough to render a simple query builder with a measure select. Here’s how it looks in the CodeSandbox:

Similar to measuresavailableMeasures, and updateMeasures, there are properties to render and manage dimensions, segments, time, filters, and chart types. You can find the full list of properties in the documentation.

Also, it is worth checking the source code of a more complicated query builder from Cube.js Playground. You can find it on Github here.

Top 7 Most Popular Node.js Frameworks You Should Know

Top 7 Most Popular Node.js Frameworks You Should Know

Node.js is an open-source, cross-platform, runtime environment that allows developers to run JavaScript outside of a browser. In this post, you'll see top 7 of the most popular Node frameworks at this point in time (ranked from high to low by GitHub stars).

Node.js is an open-source, cross-platform, runtime environment that allows developers to run JavaScript outside of a browser.

One of the main advantages of Node is that it enables developers to use JavaScript on both the front-end and the back-end of an application. This not only makes the source code of any app cleaner and more consistent, but it significantly speeds up app development too, as developers only need to use one language.

Node is fast, scalable, and easy to get started with. Its default package manager is npm, which means it also sports the largest ecosystem of open-source libraries. Node is used by companies such as NASA, Uber, Netflix, and Walmart.

But Node doesn't come alone. It comes with a plethora of frameworks. A Node framework can be pictured as the external scaffolding that you can build your app in. These frameworks are built on top of Node and extend the technology's functionality, mostly by making apps easier to prototype and develop, while also making them faster and more scalable.

Below are 7of the most popular Node frameworks at this point in time (ranked from high to low by GitHub stars).

Express

With over 43,000 GitHub stars, Express is the most popular Node framework. It brands itself as a fast, unopinionated, and minimalist framework. Express acts as middleware: it helps set up and configure routes to send and receive requests between the front-end and the database of an app.

Express provides lightweight, powerful tools for HTTP servers. It's a great framework for single-page apps, websites, hybrids, or public HTTP APIs. It supports over fourteen different template engines, so developers aren't forced into any specific ORM.

Meteor

Meteor is a full-stack JavaScript platform. It allows developers to build real-time web apps, i.e. apps where code changes are pushed to all browsers and devices in real-time. Additionally, servers send data over the wire, instead of HTML. The client renders the data.

The project has over 41,000 GitHub stars and is built to power large projects. Meteor is used by companies such as Mazda, Honeywell, Qualcomm, and IKEA. It has excellent documentation and a strong community behind it.

Koa

Koa is built by the same team that built Express. It uses ES6 methods that allow developers to work without callbacks. Developers also have more control over error-handling. Koa has no middleware within its core, which means that developers have more control over configuration, but which means that traditional Node middleware (e.g. req, res, next) won't work with Koa.

Koa already has over 26,000 GitHub stars. The Express developers built Koa because they wanted a lighter framework that was more expressive and more robust than Express. You can find out more about the differences between Koa and Express here.

Sails

Sails is a real-time, MVC framework for Node that's built on Express. It supports auto-generated REST APIs and comes with an easy WebSocket integration.

The project has over 20,000 stars on GitHub and is compatible with almost all databases (MySQL, MongoDB, PostgreSQL, Redis). It's also compatible with most front-end technologies (Angular, iOS, Android, React, and even Windows Phone).

Nest

Nest has over 15,000 GitHub stars. It uses progressive JavaScript and is built with TypeScript, which means it comes with strong typing. It combines elements of object-oriented programming, functional programming, and functional reactive programming.

Nest is packaged in such a way it serves as a complete development kit for writing enterprise-level apps. The framework uses Express, but is compatible with a wide range of other libraries.

LoopBack

LoopBack is a framework that allows developers to quickly create REST APIs. It has an easy-to-use CLI wizard and allows developers to create models either on their schema or dynamically. It also has a built-in API explorer.

LoopBack has over 12,000 GitHub stars and is used by companies such as GoDaddy, Symantec, and the Bank of America. It's compatible with many REST services and a wide variety of databases (MongoDB, Oracle, MySQL, PostgreSQL).

Hapi

Similar to Express, hapi serves data by intermediating between server-side and client-side. As such, it's can serve as a substitute for Express. Hapi allows developers to focus on writing reusable app logic in a modular and prescriptive fashion.

The project has over 11,000 GitHub stars. It has built-in support for input validation, caching, authentication, and more. Hapi was originally developed to handle all of Walmart's mobile traffic during Black Friday.

Node.js for Beginners - Learn Node.js from Scratch (Step by Step)

Node.js for Beginners - Learn Node.js from Scratch (Step by Step)

Node.js for Beginners - Learn Node.js from Scratch (Step by Step) - Learn the basics of Node.js. This Node.js tutorial will guide you step by step so that you will learn basics and theory of every part. Learn to use Node.js like a professional. You’ll learn: Basic Of Node, Modules, NPM In Node, Event, Email, Uploading File, Advance Of Node.

Node.js for Beginners

Learn Node.js from Scratch (Step by Step)

Welcome to my course "Node.js for Beginners - Learn Node.js from Scratch". This course will guide you step by step so that you will learn basics and theory of every part. This course contain hands on example so that you can understand coding in Node.js better. If you have no previous knowledge or experience in Node.js, you will like that the course begins with Node.js basics. otherwise if you have few experience in programming in Node.js, this course can help you learn some new information . This course contain hands on practical examples without neglecting theory and basics. Learn to use Node.js like a professional. This comprehensive course will allow to work on the real world as an expert!
What you’ll learn:

  • Basic Of Node
  • Modules
  • NPM In Node
  • Event
  • Email
  • Uploading File
  • Advance Of Node

20. Node.js Lessons. Data Streams in Node.JS, fs.ReadStream

20. Node.js Lessons. Data Streams in Node.JS, fs.ReadStream

20. Node.js Lessons. Data Streams in Node.JS, fs.ReadStream

Hey all! Our topic for today is Data Streams In Node.js. We will try to learn all the aspects in details for the reason it turns out that on the one hand, common browser JavaScript development lack streams. And on the other hand, knowing and understanding stream principles is necessary for seamless server development because a stream is a versatile way of work with data sources universally used.

We can define two general stream types. The first one is

stream.Readable

It is a built-in class providing streams for reading. Generally, this type itself is never used, while its descendants are quite popular – in particular, we use fs.ReadStream to read from a file. To read from a visitor’s request for its handling, there is a special object familiar to us under its name req, which is the first argument of a request handler.

Stream.Writable

It is a versatile writing method. The very stream.Writable is rarely used, but its descendants – fs.WriteStream and res – are quite common.

There are some other stream types, but the most popular are these two and their variations.

The best way to understand streams is to see how they work in practice. So, right now we’ll start with using fs.ReadStream for reading a file. Let us create a file fs.js:

var fs = require('fs');
 
// fs.ReadStream nherits from stream.Readable
var stream = new fs.ReadStream(__filename);
 
stream.on('readable', function() {
    var data = stream.read();
    console.log(data);
});
 
stream.on('end', function() {
    console.log("THE END");
});

So, we get the module fs connected and create a stream:

var fs = require('fs');
 
var stream = new fs.ReadStream(__filename);

Stream is a JavaScript object receiving information about our resource – in our case, it is a path to the file (__filename) – which can work with this resource. fs.ReadStream implements a standard reading interface described in the stream.Readable class. Let us have a detailed look.

When a stream object new stream.Readable is created, it gets connected to the data source, which is file in our case, and tries to start reading from it. Once it has read something, it imitates the event readable. This event means that all the data have been computed and are contained within an inner stream buffer that can be received using the call read(). Then we can do something with data and wait for the next readable. This cycle will be the same.

Whenever the data source gets empty (however, there are certain sources that never get empty – for example, a random data generator), the file size is limited, so we will have the end, event in the very end meaning there will be no data anymore. Moreover we can call the method destroy() at any step of working with the stream. This method means we do not need the stream anymore and it can be closed, as well as the respective data sources and everything can be cleaned up.

So, let us refer to the original code. Here we create ReadStream, and it immediately wants to open up a file:

var stream = new fs.ReadStream(__filename);

but in our case it doesn’t necessarily mean the same string because any input/output-related operation is performed through libUV. At the same time, libUV has a structure that enables all synchronous input/output handlers to get implemented during the next event loop iteration, or once the current JavaScripthas finished its work. It means, we can seamlessly use all handlers knowing that they will be installed prior to the moment the first data fragment gets read. Launch fs.js.

Look at what has appeared in the console. The first one was the event readable. It outputted data. Right now it is an ordinary buffer, but we can transform it to the string by specifying the coding directly upon the stream opening.

var stream = new fs.ReadStream(__filename, {encoding: 'utf-8'});

Thus, the modification will be automatic. When a file ends, the event endoutputs THE END in the console. Here the file ended almost immediately because it was small at the moment. Let us modify our example a little bit by making a file big.html out of the current file contained in the current directory. Download this HTML file from our repository together with the other lesson materials.

Launch it. The file big.html is big, so the event readable has been initiated several times, and every time we received another data fragment as a buffer. So, let us calculate its length:

var fs = require('fs');
 
// fs.ReadStream nherits from stream.Readable
var stream = new fs.ReadStream("big.html");
 
stream.on('readable', function() {
    var data = stream.read();
    if (data){
        console.log(data.length);
    }
    else {
        console.log('data is null')
    }
});
 
stream.on('end', function() {
    console.log("THE END");
});

Get it launched. These numbers are the read file fragment length. When a stream opens a file, it reads only its part, but not the whole file, and inserts it into its internal variable. The maximum size is exactly 64 KB. Until we call stream.Read, it won’t read further. Once we’ve received the data, the internal buffer cleans up and can be ready for reading another abstract, etc. The last abstract length is 60,959 B. This example has vividly demonstrated the key advantages of stream usage. They help save memory. Whatever is the size our big file, we still handle only its small part at a moment. The second less obvious advantage is versatility of its interface. Here we use the stream ReadStream from the file. But we can replace it any time by any stream from our resource:

var stream = new OurStream("our resource");

It won’t need any change of the left code because streams are, first of all, our interface. So, it means, if theoretically our stream performs all needed events and methods – in particular, it inherits from stream.Readable – everything should be ok. Of course, it will happen only if we do not use any special abilities that only file streams have got. To be more specific, the stream fs.ReadStream has extra events

Here we can see a draft exactly for fs.ReadStream, new events are colored in red. First, it is a file opening, while the last event is its closure. Focus your attention on the fact that if a file is read till its end, the end event occurs followed by close. And if a file is not entirely read – for instance, because of an error or upon calling the destroy method – there will be no end because the file hasn’t been ended. But the event close is always ensured upon a file closure.

Finally, our last, but not least detail here is error handling. So, let us see what will happen, if there is no file.

var stream = new fs.ReadStream("noFile.html");

So, I get it launched. Oops! It crashed! Pay your attention to the fact the streams inherit from EventEmitter. If an error occurs, the whole Node.js process fails. It happens if an error of this kind does not have any handler. That’s why if we do not want our Node.js to fail because of an exception, we should install a handler:

var fs = require('fs');
 
// fs.ReadStream nherits from stream.Readable
var stream = new fs.ReadStream("noFile.html");
 
stream.on('readable', function() {
    var data = stream.read();
    if (data){
        console.log(data.length);
    }
    else {
        console.log('data is null')
    }
});
 
stream.on('error', function(err) {
    if (err.code == 'ENOENT') {
        console.log("File not Found");
    } else {
        console.error(err);
    }
});

So, we use streams to work with data sources in Node.js. Here we’ve analyzed a basic scheme, according to which they work, and a particular example – fs.ReadStream – that can read from a file.

This lesson’s coding can be found in our repository.