Roy E Huaman

Roy E Huaman

1573267921

React's Context API Tutorial: What Context is and How to use it!

React’s Context API has become the state management tool of choice for many, oftentimes replacing Redux altogether. In this quick tutorial, you’ll see an introduction to what Context is and how to use it!

Consider this tree, in which the bottom boxes represent separate components:

Component tree

We can easily add state to the bottom components, but until now the only way to pass data to a component’s sibling was to move state to a higher component and then pass it back down to the sibling via props.

Passing data via props

If we later find out that the sibling of the component with state also needs the data, we have to lift state up again, and pass it back down:

Passing state down through multiple levels

While this solution does work, problems begin if a component on a different branch needs the data:

More distant component requires data

In this case, we need to pass state from the top level of the application through all the intermediary components to the one which needs the data at the bottom, even though the intermediary levels don’t need it. This tedious and time-consuming process is known as prop drilling.

Prop drilling

This is where Context API comes in. It provides a way of passing data through the component tree via a Provider-Consumer pair without having to pass props down through every level. Think of it as the components playing Catch with data - the intermediary components might not even “know” that anything is happening:

Context in action

To demonstrate this, we will create this funky (and super useful) day-to-night switching image.

If you want to see the full code, be sure to check out the Scrimba playground for this article.

Create Context

To begin, we create a new Context. As we want the entire app to have access to this, we go to index.js and wrap the app in ThemeContext.Provider.

We also pass the value prop to our Provider. This holds the data we want to save. For now, we just hardcode in 'Day'.

import React from "react";
import ReactDOM from "react-dom";
import ThemeContext from "./themeContext";

import App from "./App";

ReactDOM.render(
  <ThemeContext.Provider value={"Day"}>
    <App />
  </ThemeContext.Provider>,
  document.getElementById("root")
);

Consuming Context with contextType

Currently, in App.js, we are simply returning the <Image /> component.

import React from "react";
import Image from "./Image";

class App extends React.Component {
  render() {
    return (
      <div className="app">
        <Image />
      </div>
    );
  }
}

export default App;

Our goal is to use Context to switch the classNames in Image.js from Day to Night, depending on which image we want to render. To do this, we add a static property to our component called ContextType and then use string interpolation to add it to the classNames in the <Image /> component.

Now, the classNames contain the string from the value prop. Note: I have moved ThemeContext into its own file to prevent a bug.

import React from "react";
import Button from "./Button";
import ThemeContext from "./themeContext";

class Image extends React.Component {
  render() {
    const theme = this.context;
    return (
      <div className={`${theme}-image image`}>
        <div className={`${theme}-ball ball`} />
        <Button />
      </div>
    );
  }
}

Image.contextType = ThemeContext;

export default Image;

Context.Consumer

Unfortunately, this approach only works with class-based components. If you’ve learned about Hooks in React already, you’ll know we can do just about anything with functional components these days. So for good measure, we should convert our components into functional components and then use ThemeContext.Consumer component to pass info through the app.

This is done by wrapping our elements in an instance of <ThemeContext.Consumer> and within that (where the children go), providing a function which returns the elements. This uses the “render prop” pattern where we provide a regular function as a child that returns some JSX to render.

import React from "react";
import Button from "./Button";
import ThemeContext from "./themeContext";

function Image(props) {
  // We don't need this anymore
  // const theme = this.context

  return (
    <ThemeContext.Consumer>
      {theme => (
        <div className={`${theme}-image image`}>
          <div className={`${theme}-ball ball`} />
          <Button />
        </div>
      )}
    </ThemeContext.Consumer>
  );
}

// We don't need this anymore
// Image.contextType = ThemeContext;

export default Image;

Note: We also need to wrap the <Button /> component in <ThemeContext.Consumer> - this allows us to add functionality to the button later.

import React from "react";
import ThemeContext from "./themeContext";

function Button(props) {
  return (
    <ThemeContext.Consumer>
      {context => (
        <button className="button">
          Switch
          <span role="img" aria-label="sun">
            🌞
          </span>
          <span role="img" aria-label="moon">
            🌚
          </span>
        </button>
      )}
    </ThemeContext.Consumer>
  );
}

export default Button;

Extract Context Provider

We are currently passing a hard-coded value down through the Provider, however, our goal is to switch between night and day with our button.

This requires moving our Provider to a separate file and putting it in its own component, in this case, called ThemeContextProvider.

import React, { Component } from "react";
const { Provider, Consumer } = React.createContext();

class ThemeContextProvider extends Component {
  render() {
    return <Provider value={"Day"}>{this.props.children}</Provider>;
  }
}

export { ThemeContextProvider, Consumer as ThemeContextConsumer };

Note: the value property is now being handled in the new file ThemeContext.js, and should, therefore, be removed from index.js.

Changing Context
To wire up the button, we first add state to ThemeContextProvider:

import React, { Component } from "react";
const { Provider, Consumer } = React.createContext();

// Note: You could also use hooks to provide state and convert this into a functional component.
class ThemeContextProvider extends Component {
  state = {
    theme: "Day"
  };
  render() {
    return <Provider value={"Day"}>{this.props.children}</Provider>;
  }
}

export { ThemeContextProvider, Consumer as ThemeContextConsumer };

Next, we add a method for switching between day and night:

toggleTheme = () => {
  this.setState(prevState => {
    return {
      theme: prevState.theme === "Day" ? "Night" : "Day"
    };
  });
};

Now we change our value property to this.state.theme so that it returns the info from state.

 render() {
    return <Provider value={this.state.theme}>{this.props.children}</Provider>;
  }
}

Next, we change value to an object containing {theme: this.state.theme, toggleTheme: this.toggleTheme}, and update all the places where we use a single value to look for theme in an object. This means that every theme becomes context and every reference to theme as value becomes context.theme.

Finally, we tell the button to listen for the onClick event and then fire context.toggleTheme - this updates the Consumers which are using the state from the Provider. The code for the button looks like this:

import React from "react";
import { ThemeContextConsumer } from "./themeContext";

function Button(props) {
  return (
    <ThemeContextConsumer>
      {context => (
        <button onClick={context.toggleTheme} className="button">
          Switch
          <span role="img" aria-label="sun">
            🌞
          </span>
          <span role="img" aria-label="moon">
            🌚
          </span>
        </button>
      )}
    </ThemeContextConsumer>
  );
}

export default Button;

Our button now switches the image between night and day in one click!

Context caveats

Like all good things in code, there are some caveats to using Context:

  • Don’t use Context to avoid drilling props down just one or two layers. Context is great for managing state which is needed by large portions of an application. However, prop drilling is faster if you are just passing info down a couple of layers.

  • Avoid using Context to save state that should be kept locally. So if you need to save a user’s form inputs, for example, use local state and not Context.

  • Always wrap the Provider around the lowest possible common parent in the tree - not the app’s highest-level component. No need for overkill.

  • Lastly, if you pass an object as your value prop, monitor performance and refactor as necessary. This probably won’t be needed unless a drop in performance is noticeable.

Wrap up

This example is pretty simple and it would probably be easier to put state in the app and pass it down via props. However, it hopefully shows the power of having Consumers which can access data independently of the components above them in the tree.

Happy coding :)

#react-js #react #react-hooks #javascript #api

What is GEEK

Buddha Community

React's Context API Tutorial: What Context is and How to use it!

trung ken

1573636042

I have Warning: Image: Function components do not support contextType.

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.

#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

Sival Alethea

Sival Alethea

1624302000

APIs for Beginners - How to use an API (Full Course / Tutorial)

What is an API? Learn all about APIs (Application Programming Interfaces) in this full tutorial for beginners. You will learn what APIs do, why APIs exist, and the many benefits of APIs. APIs are used all the time in programming and web development so it is important to understand how to use them.

You will also get hands-on experience with a few popular web APIs. As long as you know the absolute basics of coding and the web, you’ll have no problem following along.
⭐️ Unit 1 - What is an API
⌨️ Video 1 - Welcome (0:00:00)
⌨️ Video 2 - Defining Interface (0:03:57)
⌨️ Video 3 - Defining API (0:07:51)
⌨️ Video 4 - Remote APIs (0:12:55)
⌨️ Video 5 - How the web works (0:17:04)
⌨️ Video 6 - RESTful API Constraint Scavenger Hunt (0:22:00)

⭐️ Unit 2 - Exploring APIs
⌨️ Video 1 - Exploring an API online (0:27:36)
⌨️ Video 2 - Using an API from the command line (0:44:30)
⌨️ Video 3 - Using Postman to explore APIs (0:53:56)
⌨️ Video 4 - Please please Mr. Postman (1:03:33)
⌨️ Video 5 - Using Helper Libraries (JavaScript) (1:14:41)
⌨️ Video 6 - Using Helper Libraries (Python) (1:24:40)

⭐️ Unit 3 - Using APIs
⌨️ Video 1 - Introducing the project (1:34:18)
⌨️ Video 2 - Flask app (1:36:07)
⌨️ Video 3 - Dealing with API Limits (1:50:00)
⌨️ Video 4 - JavaScript Single Page Application (1:54:27)
⌨️ Video 5 - Moar JavaScript and Recap (2:07:53)
⌨️ Video 6 - Review (2:18:03)
📺 The video in this post was made by freeCodeCamp.org
The origin of the article: https://www.youtube.com/watch?v=GZvSYJDk-us&list=PLWKjhJtqVAblfum5WiQblKPwIbqYXkDoC&index=5
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Thanks for visiting and watching! Please don’t forget to leave a like, comment and share!

#apis #apis for beginners #how to use an api #apis for beginners - how to use an api #application programming interfaces #learn all about apis

Ray  Patel

Ray Patel

1623377040

How to Validate and Geocode a Street Address in Java

When working with location services, it is important that the information you collect is accurate for your users or clients. Find out more!

When working with location services, it is important that the information you collect is accurate for your users or clients. This will prevent any mistakes in shipping, billing, and many other aspects of operations that rely on correct location information. For businesses that have applications using location services, this is especially important as any incorrect data can mean the displacement of goods or interrupted services.

The following APIs will allow you to fully validate street addresses by first parsing address data input and then verifying and normalizing the information. The last two APIs will also allow you to geocode and reverse geocode an address to receive more accurate location data for your applications.

#tutorial #api #address #java api #validation and verification #api access keys #api tutorial #validate #java api tutorials #api tutorials

Samanta  Moore

Samanta Moore

1621111320

How to Validate an Email Address in Java

Email is one of the most universal tools for sharing and receiving information across the globe, with users able to connect with others online with almost no compatibility or access issues. Using this tool, information can be instantly and securely sent to partners on the other side of the world, and personal information can be verified without divulging sensitive data about a user.

Along with this widespread use, however, comes key security measures that must take place in order to ensure the safety of your organization and data. This is particularly the case when receiving email information from previously unknown sources. These risks can include phishing attempts, malware, and other threats that can cause a negative impact to your business. Furthermore, when receiving an email address via account forms and user sign up information, you need to check that the information you are given is not only correct and real, but also that it does not lead to any malicious sources that could harm your organizational security.

The following APIs will allow you to instantly verify and validate an input email address without sending any kind of notification to the email user. This will help protect your organization in the event of any threats. The goal of this tutorial is to provide you with the tools to protect your organization’s information while providing a way to verify new accounts and user information.

This will be done through three separate functions. The first will analyze the validity of an email address’ syntax. The second will check for the address’ servers, and the third performs a full email address validation including returning the results for the previous two functions.

#java #api #java api #api access keys #api tutorial #email verification #email validation #java api tutorials #java apis #api tutorials

Top 10 API Security Threats Every API Team Should Know

As more and more data is exposed via APIs either as API-first companies or for the explosion of single page apps/JAMStack, API security can no longer be an afterthought. The hard part about APIs is that it provides direct access to large amounts of data while bypassing browser precautions. Instead of worrying about SQL injection and XSS issues, you should be concerned about the bad actor who was able to paginate through all your customer records and their data.

Typical prevention mechanisms like Captchas and browser fingerprinting won’t work since APIs by design need to handle a very large number of API accesses even by a single customer. So where do you start? The first thing is to put yourself in the shoes of a hacker and then instrument your APIs to detect and block common attacks along with unknown unknowns for zero-day exploits. Some of these are on the OWASP Security API list, but not all.

Insecure pagination and resource limits

Most APIs provide access to resources that are lists of entities such as /users or /widgets. A client such as a browser would typically filter and paginate through this list to limit the number items returned to a client like so:

First Call: GET /items?skip=0&take=10 
Second Call: GET /items?skip=10&take=10

However, if that entity has any PII or other information, then a hacker could scrape that endpoint to get a dump of all entities in your database. This could be most dangerous if those entities accidently exposed PII or other sensitive information, but could also be dangerous in providing competitors or others with adoption and usage stats for your business or provide scammers with a way to get large email lists. See how Venmo data was scraped

A naive protection mechanism would be to check the take count and throw an error if greater than 100 or 1000. The problem with this is two-fold:

  1. For data APIs, legitimate customers may need to fetch and sync a large number of records such as via cron jobs. Artificially small pagination limits can force your API to be very chatty decreasing overall throughput. Max limits are to ensure memory and scalability requirements are met (and prevent certain DDoS attacks), not to guarantee security.
  2. This offers zero protection to a hacker that writes a simple script that sleeps a random delay between repeated accesses.
skip = 0
while True:    response = requests.post('https://api.acmeinc.com/widgets?take=10&skip=' + skip),                      headers={'Authorization': 'Bearer' + ' ' + sys.argv[1]})    print("Fetched 10 items")    sleep(randint(100,1000))    skip += 10

How to secure against pagination attacks

To secure against pagination attacks, you should track how many items of a single resource are accessed within a certain time period for each user or API key rather than just at the request level. By tracking API resource access at the user level, you can block a user or API key once they hit a threshold such as “touched 1,000,000 items in a one hour period”. This is dependent on your API use case and can even be dependent on their subscription with you. Like a Captcha, this can slow down the speed that a hacker can exploit your API, like a Captcha if they have to create a new user account manually to create a new API key.

Insecure API key generation

Most APIs are protected by some sort of API key or JWT (JSON Web Token). This provides a natural way to track and protect your API as API security tools can detect abnormal API behavior and block access to an API key automatically. However, hackers will want to outsmart these mechanisms by generating and using a large pool of API keys from a large number of users just like a web hacker would use a large pool of IP addresses to circumvent DDoS protection.

How to secure against API key pools

The easiest way to secure against these types of attacks is by requiring a human to sign up for your service and generate API keys. Bot traffic can be prevented with things like Captcha and 2-Factor Authentication. Unless there is a legitimate business case, new users who sign up for your service should not have the ability to generate API keys programmatically. Instead, only trusted customers should have the ability to generate API keys programmatically. Go one step further and ensure any anomaly detection for abnormal behavior is done at the user and account level, not just for each API key.

Accidental key exposure

APIs are used in a way that increases the probability credentials are leaked:

  1. APIs are expected to be accessed over indefinite time periods, which increases the probability that a hacker obtains a valid API key that’s not expired. You save that API key in a server environment variable and forget about it. This is a drastic contrast to a user logging into an interactive website where the session expires after a short duration.
  2. The consumer of an API has direct access to the credentials such as when debugging via Postman or CURL. It only takes a single developer to accidently copy/pastes the CURL command containing the API key into a public forum like in GitHub Issues or Stack Overflow.
  3. API keys are usually bearer tokens without requiring any other identifying information. APIs cannot leverage things like one-time use tokens or 2-factor authentication.

If a key is exposed due to user error, one may think you as the API provider has any blame. However, security is all about reducing surface area and risk. Treat your customer data as if it’s your own and help them by adding guards that prevent accidental key exposure.

How to prevent accidental key exposure

The easiest way to prevent key exposure is by leveraging two tokens rather than one. A refresh token is stored as an environment variable and can only be used to generate short lived access tokens. Unlike the refresh token, these short lived tokens can access the resources, but are time limited such as in hours or days.

The customer will store the refresh token with other API keys. Then your SDK will generate access tokens on SDK init or when the last access token expires. If a CURL command gets pasted into a GitHub issue, then a hacker would need to use it within hours reducing the attack vector (unless it was the actual refresh token which is low probability)

Exposure to DDoS attacks

APIs open up entirely new business models where customers can access your API platform programmatically. However, this can make DDoS protection tricky. Most DDoS protection is designed to absorb and reject a large number of requests from bad actors during DDoS attacks but still need to let the good ones through. This requires fingerprinting the HTTP requests to check against what looks like bot traffic. This is much harder for API products as all traffic looks like bot traffic and is not coming from a browser where things like cookies are present.

Stopping DDoS attacks

The magical part about APIs is almost every access requires an API Key. If a request doesn’t have an API key, you can automatically reject it which is lightweight on your servers (Ensure authentication is short circuited very early before later middleware like request JSON parsing). So then how do you handle authenticated requests? The easiest is to leverage rate limit counters for each API key such as to handle X requests per minute and reject those above the threshold with a 429 HTTP response. There are a variety of algorithms to do this such as leaky bucket and fixed window counters.

Incorrect server security

APIs are no different than web servers when it comes to good server hygiene. Data can be leaked due to misconfigured SSL certificate or allowing non-HTTPS traffic. For modern applications, there is very little reason to accept non-HTTPS requests, but a customer could mistakenly issue a non HTTP request from their application or CURL exposing the API key. APIs do not have the protection of a browser so things like HSTS or redirect to HTTPS offer no protection.

How to ensure proper SSL

Test your SSL implementation over at Qualys SSL Test or similar tool. You should also block all non-HTTP requests which can be done within your load balancer. You should also remove any HTTP headers scrub any error messages that leak implementation details. If your API is used only by your own apps or can only be accessed server-side, then review Authoritative guide to Cross-Origin Resource Sharing for REST APIs

Incorrect caching headers

APIs provide access to dynamic data that’s scoped to each API key. Any caching implementation should have the ability to scope to an API key to prevent cross-pollution. Even if you don’t cache anything in your infrastructure, you could expose your customers to security holes. If a customer with a proxy server was using multiple API keys such as one for development and one for production, then they could see cross-pollinated data.

#api management #api security #api best practices #api providers #security analytics #api management policies #api access tokens #api access #api security risks #api access keys