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React News Monday, May 14 Error boundaries, React component tree, Context api & more…


What’s new?

  • class App extends Component { – render() { – return ( – div – h1Dashboard/h1 – /div – ) – } – }createPortal()I will use the {ReactDOM.createPortal()} below the h1 tag.
  • This function accepts two arguments: – The new subtree containing componentHere I will create a div element containing the text Welcome.
  • The App component will then look like this: – class App extends Component { – render() { – return ( – div – h1Dashboard/h1 – {ReactDOM.createPortal( – divWelcome/div, – )} – /div – ); – } – }Inside public/index.
  • class Overlay extends Component { – constructor(props) { – super(props); – this.overlayContainer = } – render() { – return ReactDOM.createPortal( – div this.overlayContainer – ); – } – }I am creating an overlayContainer inside the components constructor method.
  • render() { – return ( – div – h1Dashboard/h1 – {this.state.overlayActive – Overlay onClose={this.closeOverlay} – divWelcome/div – /Overlay} – /div – ); – }Run the yarn start command and you will see it work perfectly!

Tags: error boundaries, error boundary, React component tree, a.k.a React Fiber, fallback UI


  • The state of the entire app is store in a single object tree within a single store.To change the state, you need to trigger an action that describes what needs to happen.You should never mutate the state directly, always return a new object to do so.Lets build a simple React…
  • Create a new file named actions.js and write the following code inside it: – With that taken care of, we need to hook our Actions to the App.
  • Provider uses the older Context API and an higher order component (HOC) called connect to access different properties and make them available to different child components of the app through props.
  • In your App.js file, replace the export statement with this: – export default connect(store = store, actions)(App);With this, the connect function will now return a new component that will make the Store and Actions available to App as props.
  • If you now run yarn start or npm start, you should see something like this: – You can look at the entire source code of the Redux version of the app here.

Tags: context api, React Context API, redux, new context api,


  • If we were to write this function in a classic iterative fashion it would look something like this: – // iterative way – const sumBelow = number = { – let result = 0 for(let i = 0; i = number; i++) { – result += i – } -…
  • sum – : sumBelow(number – 1, sum + number) – )The secret sauce to recursion lies at the end of our sumBelow function, where we call sumBelow from within sumBelow.
  • In many cases, recursion can lead to more declarative, self-descriptive code youre not explaining how you get the value as with iterative code, youre describing what the final result of the function should be.
  • This means that when we have a recursive function we could actually crash the JavaScript engine!
  • sumBelow(100000);// Uncaught RangeError: Maximum call stack size exceededThe recursive function keeps adding entries to the JavaScript engines call stack until theres no more room, and then we get an error (if you want to read a bit more about how the call stack works, feel free to check out this…

Tags: recursive function, recursion, functional style, functional programming, recursive function piece


  • This Lambda training course is for JavaScript coders who want to learn to rapidly create, prototype and deploy applications and/or microservices on AWS Lambda using: – – You will use the API Gateway to call and control your Lambda functions.
  • Using the JavaScript programming language and Node.js as backend, you will be able to write and deploy real world microservices.
  • TAKE THIS COURSE – – For those who are new to AWS Lambda, it is a compute service that lets you run code (written up as Lambda functions) without provisioning or managing servers.
  • Hybrid Cloud is becoming the de facto standard for enterprise infrastructure and AWS Lambda is gaining a major and attractive share in this segment: – – So far in 2017, an average of 3 millions of new questions are asked per year on Stack Overflow.
  • AWS Lambda was tagged 3,000 times.

Tags: AWS Lambda, Lambda training course, Lambda functions, AWS sandbox, major credit cards


  • Getter and Setter methods get and set the properties of an object.
  • The setter here makes sure only valid values are added to a particular property, validity here is for the value to be a number, but what happen when we try to add a string to this property?
  • lets see what happens, change the string in the previous code to any number of your choice; – – From the above image, our value was accepted as valid and also the value of the age property was modified successfully.
  • Getters are used to get the property value inside of an object.
  • Adding a getter method to our previous example, we would have something like; – – Running the above code we have; – – In Summary: – – and methods allow you to process data before accessing or setting property values.

Tags: common object paradigm, right value. lets, setter method, Setter methods, getter method


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