Object.keys preserves key order. I’ve never (will never) depend on, but good to know …

  • However, this breaks down in one situation: if you have two sets of children that you need to reorder, there’s no way to put a key on each set without adding a wrapper element.
  • That is, if you have a component such as: – – The children will unmount and remount as you change the prop because there aren’t any keys marked on the two sets of children.
  • To solve this problem, you can use the add-on to give keys to the sets of children.
  • Instead of creating arrays, we write: – – The keys of the passed object (that is, and ) are used as keys for the entire set of children, and the order of the object’s keys is used to determine the order of the rendered children.
  • Note also that we’re relying on the JavaScript engine preserving object enumeration order here, which is not guaranteed by the spec but is implemented by all major browsers and VMs for objects with non-numeric keys.

In most cases, you can use the key prop to specify keys on the elements you’re returning from render. However, this breaks down in one situation: if you have two sets of children that you need to reorder, there’s no way to put a key on each set without adding a wrapper element.
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…”

How to use React’s Provider Pattern

How to use React's Provider Pattern  #reactjs #webdev

  • Therefore you could use React’s context to give every component access to the colored theme.
  • That way every component that needs to be styled according to the colored theme could get the necessary information from React’s context object.
  • You have the Provider component that makes properties accessible in React’s context and components that consume the context.
  • This Provider component uses React’s context to pass down the state implicitly.
  • You provide the state to your component as props, the component wraps it into React’s context and all child components can access the state by using a higher order component such as from the react-redux library.

This article gives you a walkthrough for React’s provider pattern. After reading it, you should be able to implement…
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Sharing stateful UI logic in React apps using Render Callback components

Sharing stateful UI logic in React apps using Render Callback components



#ReactJS

  • We have three components: an Accordion , Modal , and Thumbnail .
  • We could write each of them as a stateful class component with the same wrapping code, but since they have the same state setup – let’s share it!
  • Let’s abstract the state into a Toggle component (a Render Callback).
  • Now components that use Toggle will have access to their own isOpen and handleToggleClick arguments without having to wire up the state code.
  • The instances of Toggle (Accordion , Modal , and Thumbnail ) can just be stateless function components.

A few examples of abstracting shared logic across multiple components using the Render Callback pattern (aka Function as Child components).
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Dealing with focus and blur in a composite widget in React

Dealing with focus and blur in a composite widget in #ReactJS:

  • I put together a silly little pen to illustrate this behavior:A pen from codepen.io that illustrates the order in which keydown, blur, focus and keyup events fire for a tab traversal.
  • So we can listen for focus and blur events at the root of a component and react to these events fired on its child nodes.A GitHub Gist illustrating a very simple React Component for a grid element that responds to blur and focus events.The gist illustrates a React Component that returns a div element with onFocus and onBlur listeners.
  • What the gist intends to demonstrate is how we can toggle the value of the boolean state property isManagingFocus based on blur and focus events that the children of the grid component will fire.The component should:Toggle isManagingFocus to true when an element inside the grid gains focusMaintain isManagingFocus as true as long as an element inside the grid has focusToggle isManagingFocus to false when no element inside the grid has focus.This behavior is achieved by waiting a “tick” on a blur event before toggling the isManagingFocus state to false.
  • The blur and focus events will happen in the same tick (under normal circumstances), allowing the component to cancel its reaction to the blur event if a focus event occurs in the next moment and clears the timeout.
  • If no focus event from an element within the grid occurs (if the user has traversed out of the grid component), then the blur event will be processed in the next tick and the grid component will toggle isManagingFocus to false.Any time we use setTimeout/clearTimeout to manage order of operations, it feels icky.

I ran into a situation a while back while build a table grid component. I need to know when focus left the containing grid component. But the grid itself never receives focus. Its cells are focused…
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Week 6: Synthesizing – Project Breathe Service Design – Medium

Week 6: Synthesizing  #javascript #react #reactjs

  • Week 6: SynthesizingThis week we shared the result and key findings of the experiment with young children and incorporated them into our interactive storybook idea.
  • In those cases, their parents corrected their activities.We also looked through a couple of asthma storybooks that Lauren brought.
  • Given the fact that children love coloring books, we combined the idea of making an interactive coloring storybook for children and a data input prompt for parents.We all agree that the storybook should be divided by 2 parts — one for parents and the other for child.
  • Parents ask their child’s asthma symptoms and their activities by time under the guideline of the storybook and input data according to his/her response.
  • At the same time, a child will interact with his/her ‘asthma hero’ and color it to make it active with his/her device.When the parents input the data, it will send directly to the doctor’s office so the doctor can see and track the child’s symptom and diagnose well.The asthma hero also will pop up when an asthma attack comes.

This week we shared the result and key findings of the experiment with young children and incorporated them into our interactive storybook idea. From the interviews, we found that children remember…
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Learn React JS from scratch

Learn React JS from scratch
☞ 

#reactjs

  • Every react app can considered a component or a collection of components which can be re-usable.
  • You can also use React to efficiently update and render components when your data changes.
  • Who uses React Adding and accessing React Library Adding and accessing React DOM Library Adding and accessing Babel compiler Using JSX Creating a React component Using props Prop Types Using props with children Working with state Handling events Using Refs Mounting components Un-Mounting Components Updating Components Creating a React App
  • I will walk you through how to create react components from scratch, review components properties, and component state, as well as the foundational parent/child relationships within React.js.
  • React.js is a an open-source JavaScript library for creating user interfaces React adopts a component based approach in developing applications.

Learn React js JavaScript framework from scratch
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React Page Transition Animations — Frontend Weekly — Medium

Create #ReactJS page transition animations:

  • Note that in the example, we are already in a child path we can’t use IndexRoute to create a mock child for React.cloneElement so it doesn’t freak out.
  • Note that switching to a child page is an asynchronous action that unmounts a current component and mounts a new component in typical use cases this is a perfect target for Enter/Leave transitions.
  • Also note that in this case I did not expect the children to go past grandchild tier I simply used the pathname as the key.
  • Two states minimum are necessary.
  • Now we know that we have to wrap child components and HTML elements in the React transition group tag for transitions states to be applied to them.

Read the full article, click here.


@ReactiveConf: “Create #ReactJS page transition animations:”


While working on my capstone project BandHaven at coding bootcamp App Academy I learned a few things about the ReactCSSTransitionGroup add…


React Page Transition Animations — Frontend Weekly — Medium