React.js <img> Tag Rendering with Multiple Fallback & Loader Support

React Image 🏝 🏖 🏜

React Image is an <img> tag replacement and hook for React.js, supporting fallback to alternate sources when loading an image fails.

React Image allows one or more images to be used as fallback images in the event that the browser couldn’t load the previous image. When using the component, you can specify any React element to be used before an image is loaded (i.e. a spinner) or in the event that the specified image(s) could not be loaded. When using the hook this can be achieved by wrapping the component with <Suspense> and specifying the fallback prop.

React Image uses the useImage hook internally which encapsulates all the image loading logic. This hook works with React Suspense by default and will suspend painting until the image is downloaded and decoded by the browser.

Getting started

To include the code locally in ES6, CommonJS, or UMD format, install react-image using npm:

npm install react-image --save

To include the code globally from a cdn:

<script src="https://unpkg.com/react-image/umd/index.js"></script>

Dependencies

react-image has no external dependencies, aside for a version of react and react-dom which support hooks and @babel/runtime.

Documentation

You can use the standalone component, documented below, or the useImage hook.

useImage():

The useImage hook allows for incorperating react-image’s logic in any component. When using the hook, the component can be wrapped in <Suspense> to keep it from rendering until the image is ready. Specify the fallback prop to show a spinner or any other component to the user while the browser is loading. The hook will throw an error if it failes to find any images. You can wrap your componenet with an Error Boundry to catch this scenario and do/show something.

Example usage:

import React, {Suspense} from 'react'
import {useImage} from 'react-image'

function MyImageComponent() {
  const {src} = useImage({
    srcList: 'https://www.example.com/foo.jpg',
  })

  return <img src={src} />
}

export default function MyComponent() {
  return (
    <Suspense>
      <MyImageComponent />
    </Suspense>
  )
}

`useImage` API:

srcList: a string or array of strings. useImage will try loading these one at a time and returns after the first one is successfully loaded
imgPromise: a promise that accepts a url and returns a promise which resolves if the image is successfully loaded or rejects if the image doesn’t load. You can inject an alternative implementation for advanced custom behaviour such as logging errors or dealing with servers that return an image with a 404 header
useSuspense: boolean. By default, useImage will tell React to suspend rendering until an image is downloaded. Suspense can be disabled by setting this to false.

returns:

src: the resolved image address
isLoading: the currently loading status. Note: this is never true when using Suspense
error: any errors ecountered, if any

Standalone component (legacy)

When possible, you should use the useImage hook. This provides for greater flexability and provides support for React Suspense.

Include react-image in your component:

import {Img} from 'react-image'

and set a source for the image:

const myComponent = () => <Img src="https://www.example.com/foo.jpg" />

will resolve to:

<img src="https://www.example.com/foo.jpg">

If the image cannot be loaded, <img> will not be rendered, preventing a “broken” image from showing.

Multiple fallback images:

When src is specified as an array, react-image will attempt to load all the images specified in the array, starting at the first and continuing until an image has been successfully loaded.

const myComponent = () => (
  <Img
    src={['https://www.example.com/foo.jpg', 'https://www.example.com/bar.jpg']}
  />
)

If an image has previously been attempted unsuccessfully, react-image will not retry loading it again until the page is reloaded.

Show a “spinner” or other element before the image is loaded:

const myComponent = () => (
  <Img
    src={['https://www.example.com/foo.jpg', 'https://www.example.com/bar.jpg']}
    loader={/*any valid react element */}
  />
)

If an image was previously loaded successfully (since the last time the page was loaded), the loader will not be shown and the image will be rendered immediately instead.

Show a fallback element if none of the images could be loaded:

const myComponent = () => (
  <Img
    src={['https://www.example.com/foo.jpg', 'https://www.example.com/bar.jpg']}
    unloader={/*any valid react element */}
  />
)

NOTE:

The following options only apply to the <Img> component, not to the useImage hook. When using the hook you can inject a custom image resolver with custom behaviour as required.

Decode before paint

By default and when supported by the browser, react-image uses Image.decode() to decode the image and only render it when it’s fully ready to be painted. While this doesn’t matter much for vector images (such as svg’s) which are rendered immediately, decoding the image before painting prevents the browser from hanging or flashing while the image is decoded. If this behaviour is undesirable, it can be disabled by setting the decode prop to false:

const myComponent = () => (
  <Img src={'https://www.example.com/foo.jpg'} decode={false} />
)

Loading images with a CORS policy

When loading images from another domain with a CORS policy, you may find you need to use the crossorigin attribute. For example:

const myComponent = () => (
  <Img src={'https://www.example.com/foo.jpg'} crossorigin="anonymous" />
)

Animations and other advanced uses

A wrapper element container can be used to facilitate higher level operations which are beyond the scope of this project. container takes a single property, children which is whatever is passed in by React Image (i.e. the final <img> or the loaders).

For example, to animate the display of the image (and animate out the loader) a wrapper can be set:

<Img
  src={'https://www.example.com/foo.jpg'}
  container={(children) => {
    return <div className="foo">{children}</div>
  }}
/>

The <img> will now be contained by the div with class foo which can be targeted via css. A crude example of a transition using ReactCSSTransitionReplace can be found here. Error reporting (i.e. logging images that loaded ok or failed to load) can be accomplished with container, too. A sample implementation can be found here.

By default, the loader and unloader components will also be wrapped by the container component. These can be set independently by passing a container via loaderContainer or unloaderContainer. To disable the loader or unloader from being wrapped, pass a noop to loaderContainer or unloaderContainer (like unloaderContainer={img => img}).

Recipes

Delay rendering until element is visible (lazy rendering)

By definition, React Image will try loading images right away. This may be undesirable in some situations, such as when the page has many images. As with any react element, rendering can be delayed until the image is actually visible in the viewport using popular libraries such as react-visibility-sensor. Here is a quick sample (psudocode/untested!):

import {Img} from 'react-image'
import VisibilitySensor from 'react-visibility-sensor'

const myComponent = () =>
  <VisibilitySensor>
    <Img src='https://www.example.com/foo.jpg'>
  </VisibilitySensor>

Note: it is not nesesary to use React Image to prevent loading of images past “the fold” (i.e. not currently visable on in the window). Instead just use the native HTML <img> element and the loading="lazy" prop. See more here.

Animate image loading

see above

License

react-image is available under the MIT License

Download Details:

Author: mbrevda

Source Code: https://github.com/mbrevda/react-image

#react #reactjs #javascript

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React.js <img> Tag Rendering with Multiple Fallback & Loader Support

Autumn Blick

1598839687

How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

Performance: It delivers optimal performance.
Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
UI design: React Native enables you to design simple and responsive UI for your mobile app.
3rd party plugins: This framework supports 3rd party plugins.
Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
Near-native user experience: React Native provides several native components, and these are platform agnostic.
The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

#android app #frontend #ios app #mobile app development #benefits of react native #is react native good for mobile app development #native vs #pros and cons of react native #react mobile development #react native development #react native experience #react native framework #react native ios vs android #react native pros and cons #react native vs android #react native vs native #react native vs native performance #react vs native #why react native #why use react native

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JavaScript Daily

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NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.

Status

Experimental. Please report issues here.

Goals and features

Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.

Additional goals and features are:

Fast startup without relying on a custom version of Node.js.
Small artifact (current size is around 1.2MB).
First class macros.
Support building small TUI apps using Reagent.
Complement babashka with libraries from the Node.js ecosystem.

Requirements

Nbb requires Node.js v12 or newer.

How does this tool work?

CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).

Usage

Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'
6

And then install some other NPM libraries to use in the script. E.g.:

$ npm install csv-parse shelljs zx

Create a script which uses the NPM libraries:

(ns script
  (:require ["csv-parse/lib/sync$default" :as csv-parse]
            ["fs" :as fs]
            ["path" :as path]
            ["shelljs$default" :as sh]
            ["term-size$default" :as term-size]
            ["zx$default" :as zx]
            ["zx$fs" :as zxfs]
            [nbb.core :refer [*file*]]))

(prn (path/resolve "."))

(prn (term-size))

(println (count (str (fs/readFileSync *file*))))

(prn (sh/ls "."))

(prn (csv-parse "foo,bar"))

(prn (zxfs/existsSync *file*))

(zx/$ #js ["ls"])

Call the script:

$ nbb script.cljs
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs

Macros

Nbb has first class support for macros: you can define them right inside your .cljs file, like you are used to from JVM Clojure. Consider the plet macro to make working with promises more palatable:

(defmacro plet
  [bindings & body]
  (let [binding-pairs (reverse (partition 2 bindings))
        body (cons 'do body)]
    (reduce (fn [body [sym expr]]
              (let [expr (list '.resolve 'js/Promise expr)]
                (list '.then expr (list 'clojure.core/fn (vector sym)
                                        body))))
            body
            binding-pairs)))

Using this macro we can look async code more like sync code. Consider this puppeteer example:

(-> (.launch puppeteer)
      (.then (fn [browser]
               (-> (.newPage browser)
                   (.then (fn [page]
                            (-> (.goto page "https://clojure.org")
                                (.then #(.screenshot page #js{:path "screenshot.png"}))
                                (.catch #(js/console.log %))
                                (.then #(.close browser)))))))))

Using plet this becomes:

(plet [browser (.launch puppeteer)
       page (.newPage browser)
       _ (.goto page "https://clojure.org")
       _ (-> (.screenshot page #js{:path "screenshot.png"})
             (.catch #(js/console.log %)))]
      (.close browser))

See the puppeteer example for the full code.

Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet macro is similar to promesa.core/let.

Startup time

$ time nbb -e '(+ 1 2 3)'
6
nbb -e '(+ 1 2 3)'   0.17s  user 0.02s system 109% cpu 0.168 total

The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx this adds another 300ms or so, so for faster startup, either use a globally installed nbb or use $(npm bin)/nbb script.cljs to bypass npx.

Dependencies

NPM dependencies

Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.

Classpath

To load .cljs files from local paths or dependencies, you can use the --classpath argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs relative to your current dir, then you can load it via (:require [foo.bar :as fb]). Note that nbb uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar in the namespace name becomes foo_bar in the directory name.

To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:

$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"

and then feed it to the --classpath argument:

$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]

Currently nbb only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar files will be added later.

Current file

The name of the file that is currently being executed is available via nbb.core/*file* or on the metadata of vars:

(ns foo
  (:require [nbb.core :refer [*file*]]))

(prn *file*) ;; "/private/tmp/foo.cljs"

(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"

Reagent

Nbb includes reagent.core which will be lazily loaded when required. You can use this together with ink to create a TUI application:

$ npm install ink

ink-demo.cljs:

(ns ink-demo
  (:require ["ink" :refer [render Text]]
            [reagent.core :as r]))

(defonce state (r/atom 0))

(doseq [n (range 1 11)]
  (js/setTimeout #(swap! state inc) (* n 500)))

(defn hello []
  [:> Text {:color "green"} "Hello, world! " @state])

(render (r/as-element [hello]))

Promesa

Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core namespace is included with the let and do! macros. An example:

(ns prom
  (:require [promesa.core :as p]))

(defn sleep [ms]
  (js/Promise.
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
  []
  (p/do!
   (println "Doing stuff which takes a while")
   (sleep 1000)
   1))

(p/let [a (do-stuff)
        b (inc a)
        c (do-stuff)
        d (+ b c)]
  (prn d))

$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while
3

Also see API docs.

Js-interop

Since nbb v0.0.75 applied-science/js-interop is available:

(ns example
  (:require [applied-science.js-interop :as j]))

(def o (j/lit {:a 1 :b 2 :c {:d 1}}))

(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1

Most of this library is supported in nbb, except the following:

destructuring using :syms
property access using .-x notation. In nbb, you must use keywords.

See the example of what is currently supported.

Examples

See the examples directory for small examples.

Also check out these projects built with nbb:

c64core: retrocompute aesthetics twitter bot
gallery.cljs: script to download walpapers from windowsonearth.org.
nbb-action-example: example of a Github action built with nbb.

API

See API documentation.

Migrating to shadow-cljs

See this gist on how to convert an nbb script or project to shadow-cljs.

Build

Prequisites:

babashka >= 0.4.0
Clojure CLI >= 1.10.3.933
Node.js 16.5.0 (lower version may work, but this is the one I used to build)

To build:

Clone and cd into this repo
bb release

Run bb tasks for more project-related tasks.

Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: https://github.com/borkdude/nbb
License: EPL-1.0

#node #javascript

Mathew Rini

1615544450

How to Select and Hire the Best React JS and React Native Developers?

Since March 2020 reached 556 million monthly downloads have increased, It shows that React JS has been steadily growing. React.js also provides a desirable amount of pliancy and efficiency for developing innovative solutions with interactive user interfaces. It’s no surprise that an increasing number of businesses are adopting this technology. How do you select and recruit React.js developers who will propel your project forward? How much does a React developer make? We’ll bring you here all the details you need.

What is React.js?

Facebook built and maintains React.js, an open-source JavaScript library for designing development tools. React.js is used to create single-page applications (SPAs) that can be used in conjunction with React Native to develop native cross-platform apps.

React vs React Native

React Native is a platform that uses a collection of mobile-specific components provided by the React kit, while React.js is a JavaScript-based library.
React.js and React Native have similar syntax and workflows, but their implementation is quite different.
React Native is designed to create native mobile apps that are distinct from those created in Objective-C or Java. React, on the other hand, can be used to develop web apps, hybrid and mobile & desktop applications.
React Native, in essence, takes the same conceptual UI cornerstones as standard iOS and Android apps and assembles them using React.js syntax to create a rich mobile experience.

What is the Average React Developer Salary?

In the United States, the average React developer salary is $94,205 a year, or $30-$48 per hour, This is one of the highest among JavaScript developers. The starting salary for junior React.js developers is $60,510 per year, rising to $112,480 for senior roles.

* React.js Developer Salary by Country

United States- $120,000
Canada - $110,000
United Kingdom - $71,820
The Netherlands $49,095
Spain - $35,423.00
France - $44,284
Ukraine - $28,990
India - $9,843
Sweden - $55,173
Singapore - $43,801

In context of software developer wage rates, the United States continues to lead. In high-tech cities like San Francisco and New York, average React developer salaries will hit $98K and $114per year, overall.

However, the need for React.js and React Native developer is outpacing local labour markets. As a result, many businesses have difficulty locating and recruiting them locally.

It’s no surprise that for US and European companies looking for professional and budget engineers, offshore regions like India are becoming especially interesting. This area has a large number of app development companies, a good rate with quality, and a good pool of React.js front-end developers.

As per Linkedin, the country’s IT industry employs over a million React specialists. Furthermore, for the same or less money than hiring a React.js programmer locally, you may recruit someone with much expertise and a broader technical stack.

How to Hire React.js Developers?

Conduct thorough candidate research, including portfolios and areas of expertise.
Before you sit down with your interviewing panel, do some homework.
Examine the final outcome and hire the ideal candidate.

Why is React.js Popular?

React is a very strong framework. React.js makes use of a powerful synchronization method known as Virtual DOM, which compares the current page architecture to the expected page architecture and updates the appropriate components as long as the user input.

React is scalable. it utilises a single language, For server-client side, and mobile platform.

React is steady.React.js is completely adaptable, which means it seldom, if ever, updates the user interface. This enables legacy projects to be updated to the most new edition of React.js without having to change the codebase or make a few small changes.

React is adaptable. It can be conveniently paired with various state administrators (e.g., Redux, Flux, Alt or Reflux) and can be used to implement a number of architectural patterns.

Is there a market for React.js programmers?
The need for React.js developers is rising at an unparalleled rate. React.js is currently used by over one million websites around the world. React is used by Fortune 400+ businesses and popular companies such as Facebook, Twitter, Glassdoor and Cloudflare.

Final thoughts:

As you’ve seen, locating and Hire React js Developer and Hire React Native developer is a difficult challenge. You will have less challenges selecting the correct fit for your projects if you identify growing offshore locations (e.g. India) and take into consideration the details above.

If you want to make this process easier, You can visit our website for more, or else to write a email, we’ll help you to finding top rated React.js and React Native developers easier and with strives to create this operation

#hire-react-js-developer #hire-react-native-developer #react #react-native #react-js #hire-react-js-programmer

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Hire Top React JS Developers | Offshore Reactjs Programmers India

Looking to hire top dedicated Reactjs developers from India at affordable prices? Our 5+ years of average experienced Reactjs developers comprise proficiency in delivering the most complex and challenging web apps.

Planning to outsource** Reactjs development company in India** ? Or would you like to hire a team of Reactjs developers? Get in touch for a free quote!

#hire react.js developers #hire react js developers #react programmers #react js development company #react native development company #react.js developers

React.js <img> Tag Rendering with Multiple Fallback & Loader Support

React Image 🏝 🏖 🏜

Getting started

Dependencies

Documentation

useImage():

useImage API:

Standalone component (legacy)

Multiple fallback images:

Show a “spinner” or other element before the image is loaded:

Show a fallback element if none of the images could be loaded:

NOTE:

Decode before paint

Loading images with a CORS policy

Animations and other advanced uses

Recipes

Delay rendering until element is visible (lazy rendering)

Animate image loading

License

Download Details:

What is GEEK

Buddha Community

How native is React Native? | React Native vs Native App Development

A brief introduction to React Native

Why React Native is fundamentally different from earlier hybrid frameworks

Top React JS Development Company | React JS Development Services

NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Status

Goals and features

Requirements

How does this tool work?

Usage

Macros

Startup time

Dependencies

NPM dependencies

Classpath

Current file

Reagent

Promesa

Js-interop

Examples

API

Migrating to shadow-cljs

Build

How to Select and Hire the Best React JS and React Native Developers?

What is React.js?

React vs React Native

What is the Average React Developer Salary?

* React.js Developer Salary by Country

How to Hire React.js Developers?

Why is React.js Popular?

Final thoughts:

Hire Top React JS Developers | Offshore Reactjs Programmers India

`useImage` API: