· Mobile App Development with React Native

  • This course picks up where Harvard College’s CS50 leaves off, transitioning from web development to mobile app development with React Native, a popular open-source framework maintained by Facebook that enables cross-platform native apps using JavaScript without Java or Swift.
  • The course introduces students to modern JavaScript (including ES6 and ES7) as well as to JSX, a JavaScript extension.
  • Through hands-on projects, students gain experience with React and its paradigms, app architecture, and user interfaces.
  • The course culminates in a final project for which students implement an app entirely of their own design.


Jordan Hayashi

jordan@cs50.harvard.edu

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The Pros and Cons of ReactJS for your Online Business

The Pros and Cons of ReactJS for your Online Business  via @janlgordon

  • With React, it is possible for webmasters and online business owners to develop large web-based applications that change data while reloading pages.
  • Webmasters can also use React together with other forms of frameworks or JavaScript libraries like Angular in MVC.
  • It makes it possible to reuse components that didn’t produce changes, and this makes programming more comfortable and precise for online business owners.
  • The great news for webmasters is that Google might still find the React component when just the client-side is rendered.
  • ReactJS is a great framework for online business.

This isn’t quite a ReactJS guide for the layman. But it is a useful for business owners, if only to glean enough to know how to talk with your techie
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Impress Your Friends With Code Splitting in React – Hacker Noon

Impress Your Friends With #Code Splitting in #ReactJS:  by @burkeholland #JavaScript

  • Both of those actions show the edit form.First I am going to add a spot in my state for this “EditForm” component to live.class Heroes extends Component { constructor(props) { super(props); this.state = { …, lazyEditHero: null } } …, render() { return ( … ) }}I put mine in…
  • I have put this in a function called LoadEditFormclass Heroes extends Component { constructor(props) { super(props); this.state = { … lazyEditHero: null } } async LoadEditForm() { const { default : EditHero } = await import(‘.
  • /EditHero’); this.setState({ lazyEditHero: EditHero }) } render() { return ( … ) }}Now we just need to call this LoadEditForm from the two functions that trigger the editor component to be shown.class Heroes extends Component { constructor(props) { super(props); this.state = { … lazyEditHero: null } } async LoadEditForm() {…
  • /EditHero’); this.setState({ lazyEditHero: EditHero }) } handleSelect = async hero = { await this.LoadEditForm(); this.setState({ selectedHero: hero }); } handleEnableAddMode = async () = { await this.LoadEditForm(); this.setState({ addingHero: true, selectedHero: { id: ”, name: ”, saying: ” } }); } … render() { return ( … ) }}A few…
  • This also allows us to pass any props to our component when it is so lazily loaded.class Heroes extends Component { constructor(props) { super(props); this.state = { … lazyEditHero: null } } async LoadEditForm() { const { default : EditHero } = await import(‘.

In preparation for the DevUp keynote a few weeks ago, I took some time to learn the minimum amount possible to demonstrate code splitting in React. Now your first reaction is probably… As part of the…
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Writing Easily Testable Code with Stateless Components in React.js

Writing Easily Testable Code with Stateless Components in #React.JS  #javascript #testing

  • The use of Stateless Functional Components (a.k.a. “pure” or “dumb” components) in React.js continues to grow since first it was released in React 0.14, and for good reasons.
  • By relying on pure components, developers end up writing reusable code that’s extremely easy to test, which leads to better application architecture.
  • Personally, I like the term “pure component” because it’s indicative of what the code really is — a pure function sprinkled with some JSX.
  • In addition to these benefits, pure components also make it extremely easy to test code with any crazy props that you wish.
  • As we just saw, the code for functional components provides us awesome intel for everything we need to know in order to write effective tests.

Functional Stateless Components provides clean syntax that allows us to write more declarative code. We will look at stateless components and finish up with some unit tests in this article.
Continue reading “Writing Easily Testable Code with Stateless Components in React.js”

Writing Easily Testable Code with Stateless Components in React.js

  • The use of Stateless Functional Components (a.k.a. “pure” or “dumb” components) in React.js continues to grow since first it was released in React 0.14, and for good reasons.
  • By relying on pure components, developers end up writing reusable code that’s extremely easy to test, which leads to better application architecture.
  • Personally, I like the term “pure component” because it’s indicative of what the code really is — a pure function sprinkled with some JSX.
  • In addition to these benefits, pure components also make it extremely easy to test code with any crazy props that you wish.
  • As we just saw, the code for functional components provides us awesome intel for everything we need to know in order to write effective tests.

Functional Stateless Components provides clean syntax that allows us to write more declarative code. We will look at stateless components and finish up with some unit tests in this article.
Continue reading “Writing Easily Testable Code with Stateless Components in React.js”

Using JSX and React #React #reactjs #javascript #Framework #programming

Using JSX and React  #React #reactjs #javascript #Framework #programming

  • You use JSX within React code to easily create components for your apps.
  • Here is an example of JSX being used to render HTML:

    To create a component, just use a local variable that starts with an upper-case letter, e.g.:

    Note: There are reserved words in JSX, as it is essentially JavaScript after all—so keywords such as and are discouraged as attribute names.

  • Form creation is easy with JSX and sub-components, for example:

    To make this work, you must create the sub-components as attributes of the main component:

    To use some JavaScript to create a result for use in an attribute value, React just needs you to wrap it in curly braces like so:

    You can also just pass a boolean value for form attributes such as , and so on.

  • First we use to establish signalling of a new user connected via the as so:

    Then, to connect to the PeerServer, we use the following:

    We then listen for events via the method:

    We also have our JSX inside components in the directory.

  • Now it’s as simple as pushing your code to heroku:

    Once the push is finished, you will be able to start your web service with the following:

    Now just visit the URL provided, or as a shortcut use the command as so:

    You’ve learned how to create JSX components and interface them with React, with a detailed example of the chat application.

What You’ll Be CreatingJSX is similar to a mix of XML and HTML. You use JSX within React code to easily create components for your apps. JSX transforms into JavaScript when React compiles the…
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Using Semiotic if You’ve Never Used React – Elijah Meeks – Medium

  • Using Semiotic if You’ve Never Used ReactI released Semiotic to help folks using React deploy better data visualization.
  • If you’re interested in also understanding D3v4 better, my 2nd edition of D3.js in Action has a chapter on React that explains its core concepts from the perspective of a data visualization developer familiar with D3.Setting up Your React AppFor those of you coming from traditional web development with static source files included in your HTML doc, the biggest hurdle is the modern JavaScript development environment.
  • Now that you have Semiotic installed, you can import any of its components and use them almost as you see them in the interactive examples in the documentation.Using Semiotic in Your AppI say “almost” because the examples have code that look like this:const answers = [ {“question”:”Question 1″, “type”:”disagree”, “color”:”#d38779″, “value”:-294, “percent”:-0.09}, {“question”:”Question 1″, “type”:”stronglydisagree”, “color”:”#b3331d”, “value”:-24, “percent”:-0.007}, {“question”:”Question 1″, “type”:”agree”, “color”:”#00a2ce”, “value”:1927, “percent”:0.59}]import { ORFrame } from ‘semiotic’export default ORFrame size={[ 700,500 ]} data={answers} type=”bar” projection=”horizontal” oAccessor={“question”} rAccessor={“percent”} style={d = ({ fill: d.color })} margin={{ top: 30, bottom: 0, left: 80, right: 50 }} oPadding={20} oLabel={true} axis={{ orient: “top”, tickValues: [ -0.3, -0.15, 0, 0.2, 0.4, 0.6, 0.8, 1]}}/And that’s not really React ready.
  • Rather than just directly exporting or using ORFrame like you see above, you need to drop it somewhere in the render function of the component where you want to have data visualization.
  • So the real code would look more like this:import React from “react”;import { ORFrame } from ‘semiotic’const answers = const answers = [ {“question”:”Question 1″, “type”:”disagree”, “color”:”#d38779″, “value”:-294, “percent”:-0.09}, {“question”:”Question 1″, “type”:”stronglydisagree”, “color”:”#b3331d”, “value”:-24, “percent”:-0.007}, {“question”:”Question 1″, “type”:”agree”, “color”:”#00a2ce”, “value”:1927, “percent”:0.59}]export default class DivergingStackedBar extends React.Component {render() {return (divh1A diverging Bar Chart With Negative Values/h1ORFrame size={[ 700,500 ]} data={answers} type=”bar” projection=”horizontal” oAccessor={“question”} rAccessor={“percent”} style={d = ({ fill: d.color })} margin={{ top: 30, bottom: 0, left: 80, right: 50 }} oPadding={20} oLabel={true} axis={{ orient: “top”, tickValues: [ -0.3, -0.15, 0, 0.2, 0.4, 0.6, 0.8, 1]}} //div) } // End of the render function} // End of the componentYou may wonder why I put the data array outside of the render function.

I released Semiotic to help folks using React deploy better data visualization. But since announcing its release I’ve heard from a few people who want to try to develop with Semiotic but have never…
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