Charger un enregistrement de base de données existant dans un formulaire React.js

Les opérations courantes dans tout système d'information sont les opérations de création , de lecture , de mise à jour et de suppression (CRUD) sur un enregistrement de la base de données. Dans ce guide, nous verrons comment effectuer les parties de création et de mise à jour dans le contexte d'une application React.js. Le composant doit pouvoir fournir un formulaire qui traitera de la sauvegarde des informations en tant que nouvel enregistrement ou de la mise à jour d'un enregistrement existant. Dans les approches traditionnelles, pour distinguer a created'un updateprovenant d'un formulaire, la idvaleur doit être présente afin d'indiquer que les détails du formulaire effectueront une mise à jour plutôt qu'une création. Il s'agit toutefois d'un risque pour la sécurité, depuis leidest parfois exposé en tant que valeur masquée dans HTML ou dans le cadre de l'URL à laquelle se connecter. Nous verrons dans ce guide que nous pouvons utiliser l'approche de gestion d'état de React.js pour conserver la idvaleur uniquement dans la logique React.js et non dans l'interface elle-même.

Avant de commencer, faisons trois hypothèses :

  1. Nous allons conserver un objet qui modélise une personne avec un id, first_nameet last_name.
  2. React.js interagit avec une API backend exécutée dans http://localhost:3000/api/v1/people/save.
  3. Pour récupérer les données d'une personne existante, nous pouvons accéder à une API via une requête GET dans le point de terminaison http://localhost:3000/api/v1/people/fetch.

Ce guide fournira un ensemble d'instructions simples sur la façon d'implémenter le backend à l'aide de Ruby on Rails dans la section Rails Server Code à la fin. Quoi qu'il en soit, vous pouvez toujours utiliser votre propre framework préféré pour implémenter le backend qui répond aux hypothèses ci-dessus.

Création du composant de formulaire

Créez un composant initial qui conserve les états id, first_nameet last_namereflétant le modèle de données d'une personne.

import React from 'react';
import $ from 'jquery';

export default class PersonForm extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      id: props.id,
      firstName: "",
      lastName: ""
    }
  }

  updateFirstName(event) {
    this.setState({
      firstName: event.target.value 
    });
  }

  updateLastName(event) {
    this.setState({
      lastName: event.target.value 
    });
  }

  render() {
    return (
      <div>
        First Name:
        <input type="text" value={this.state.firstName} onChange={this.updateFirstName.bind(this)} />
        Last Name:
        <input type="text" value={this.state.lastName} onChange={this.updateLastName.bind(this)} />
        <hr/>

        <button>
          Save
        </button>
      </div>
    );
  }
}

Il s'agit d'un composant React.js standard qui contient une logique minimale, à savoir l'utilisation de updateFirstNameet de updateLastNameméthodes pour mettre à jour l'état firstNameet lastNamechaque fois que l'utilisateur modifie quelque chose. Notez également que dans le constructeur, vous pouvez passer un iden tant que partie de props. Cela suggère qu'il est possible de monter ce composant et de passer un an iddu parent qui l'appelle, ce qui fournira des informations pour effectuer une mise à jour. Facultativement, vous pouvez également ne pas transmettre de message idsuggérant que vous utilisez le composant pour créer un nouvel enregistrement.

Interagir avec l'API

Créez une méthode qui effectuera un POST au point de terminaison de l'API /api/v1/people/save. La méthode ressemble à ceci :

save() {
  var context = this;

  $.ajax({
    url: "http://localhost:3000/api/v1/people/save",
    method: "POST",
    data: {
      id: context.state.id,
      first_name: context.state.firstName,
      last_name: context.state.lastName
    },
    success: function(response) {
      alert("Successfully saved record!");
    },
    error: function(response) {
      alert("Error in saving record!");
    }
  });
}

Notez que vous devez d'abord créer un proxy pour thisafin de pouvoir toujours faire référence à l'instance de ce composant dans l' ajaxappel, par exemple pour accéder aux valeurs d'état actuelles context.state.id, context.state.firstNameet context.state.lastName. Cela exécutera une méthode POST sur l'API. Si non ida été fourni, il crée un enregistrement. Mais si un ida été initialement fourni au composant via props, le backend doit alors effectuer une mise à jour à la place.

Enfin, connectez la saveméthode à l' onClickattribut du bouton du composant :

<button onClick={this.save.bind(this)}>
  Save
</button>

Code du serveur Rails

Assurez-vous que vous disposez d'un serveur d'applications fonctionnant avec les spécifications mentionnées précédemment. Cette section vous permettra d'implémenter un serveur backend écrit en Ruby on Rails en utilisant la base de données sqlite afin que vous n'ayez aucune dépendance en dehors de Rails.

  1. Créez un nouveau projet.
$ rails new sampleapi
$ cd sampleapi

2. Créez un modèle pour la personne et chargez-le dans la base de données.

$ rails g model Person first_name:string last_name:string
$ rake db:migrate

3. Dans le fichier config/routes.rb, créez la définition de route d'API.

namepsace :api do
  namespace :v1 do
    get "/people/fetch", to: "people#fetch"
    post "/people/save", to: "people#save"
  end
end

4. Créez un contrôleur pour l'API dansapp/controllers/api/v1/people_controller.rb

module Api
  module V1
    class PeopleController < ApplicationController
      protect_from_forgery with: :null_session

      def fetch
        person = Person.find(params[:id])

        render json: person
      end

      def save
        person = Person.find_by_id(params[:id])

        if person.present?
          person.first_name = params[:first_name]
          person.last_name  = params[:last_name]
        else
          person = Person.new(first_name: params[:first_name], last_name: params[:last_name])
        end

        person.save!

        render json: { message: "success", id: person.id }
      end
    end
  end
end

5. Exécutez le serveur et liez-le à localhost.

$ rails server -b 127.0.0.1

Code global

Le code final devrait ressembler à ceci :

import React from 'react';
import $ from 'jquery';

export default class PersonForm extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      id: props.id,
      firstName: "",
      lastName: ""
    }
  }

  updateFirstName(event) {
    this.setState({
      firstName: event.target.value 
    });
  }

  updateLastName(event) {
    this.setState({
      lastName: event.target.value 
    });
  }

  save() {
    var context = this;

    $.ajax({
      url: "http://localhost:3000/api/v1/people/save",
      method: "POST",
      data: {
        id: context.state.id,
        first_name: context.state.firstName,
        last_name: context.state.lastName
      },
      success: function(response) {
        alert("Successfully saved record!");
      },
      error: function(response) {
        alert("Error in saving record!");
      }
    });
  }

  render() {
    return (
      <div>
        First Name:
        <input type="text" value={this.state.firstName} onChange={this.updateFirstName.bind(this)} />
        Last Name:
        <input type="text" value={this.state.lastName} onChange={this.updateLastName.bind(this)} />
        <hr/>

        <button onClick={this.save.bind(this)}>
          Save
        </button>
      </div>
    );
  }
}

Avec seulement quelques lignes de code, vous avez maintenant un composant recyclable qui traite à la fois de la création et de la mise à jour d'un enregistrement à partir d'une base de données. Bien sûr, les informations gérées dépendront en grande partie des attributs spécifiés, ainsi que des points de terminaison API auxquels se connecter. Cependant, le but de cette approche est que vous pouvez tirer parti des mécanismes de gestion d'état de React.js pour créer un formulaire avec une interface qui reflète un schéma existant dans le backend. Contrairement à d'autres approches, cela est considéré comme plus sûr puisque la idvaleur n'est jamais exposée dans l'interface utilisateur.

En tant que défi, j'ai délibérément laissé de côté la logique de récupération d'un enregistrement dans la base de données. Essayez de voir si vous pouvez écrire une méthode appelée fetch(id)avec une logique qui effectue un appel contre /api/v1/people/fetchet charge les valeurs dans le formulaire en appelant setStateinside fetch(id). Idéalement, c'est le seul ajout dont vous avez besoin car tout le reste du formulaire suivra les attributs extraits de l'API.

What is GEEK

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Autumn  Blick

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.

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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:

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

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sophia tondon

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