In a React application, we can pass data from parent component to child components using the prop. However, this is limited to certain type of properties such as Theme, locale preference, etc., which need to be used at global level in the application. With React Context, we can use the data or props without explicitly passing them as props to the component.

Context has three main elements. We need to understand these elements to utilize Context to the fullest.

1. Context Object – The Context object is designed to share data globally in the application.
2. Context Provider – The Context object comes with a provider that can be used to consume Context data in the React component.
3. Context Consumer – The Context Consumer is wrapped inside the Context provider, and it is used to get access to the Context data.

In this article, let us see how to create a Theme Context using typescript step by step.

1.Create Theme Context Object. Export ThemeContext and set the Context default value to ‘undefined’.

2.Create the Theme object by using two Themes, for instance, here we are going to use ‘dark’ and ‘light’.

3.Create Theme Context provider.

4.We created the Theme Context Provider by setting the Default Theme and function to change the Theme.

5.Subscribe Theme Context by wrapping the component with Context provider.

6.Use or set the Context data as shown in the screenshot below.

The concept of Context is simple yet effective. In this article, we covered how to use Context in the React Application with Theme Context example using TypeScript.

Should you have any queries, please contact MetaSys Software React experts, who have abundant experience in engineering applications using latest dev-tools such as React-Redux, React Hooks, React Router, React Bootstrap, etc.

You can reach out to us with any coding queries too! We would be happy to help!

Happy Coding!

There are two main aspects to internationalization, firstly the detection of the user’s local language, and secondly the modification of the content, including translation of the text, and switching relevant items such as currency.

This article addresses how to implement the internationalization of a React application using the library ‘React-intl’. The first step is to create a new React project and add the intl package:

• Create a React project using the commands –

$ npx create-react-app project_i18n

         $ cd project_i18n

• Add the ‘react-intl’ package.

Configuration of the package consists of four main steps: creating the locales, creating the provider, and finally creating a common translator. In the remainder of this article, I will elaborate on these steps.

1. Create the locales –

a.Create a folder with the name ‘i18n’ in your code folder.

b.Create a file ‘locale.js’ and export the locales object.

2. Create the provider –

a.Now, let’s create the Provider to hook the IntlProvider to the application.

In the above image, IntlProvider is imported from react-intl and a wrapper is created for the application, setting the default locale and passing the message content according to the locale.

b.To create the messages for the respective languages, create a folder called ‘MessageContent’ and create the locale files for messages within that folder.
Let us create two different message objects.
For English: – en-US.js –

For French:- fr-CA.js –

c. Create an ‘js’ file under the MessageContent folder to export the messages.
MessageContent-> index.js –

3. Create a common translator –

a.Let us create a common Translate function to translate the message according to the locale.
i18n-> translate.js –

b.Create ‘index.js’ under the ‘i18n’ folder to export the locales and provider as default.
i18n-> index.js –

c.Finally, let us wrap the application with IntlProvider and set the locale in App.js.
src-> App.js –

Example for French Locale –

fr-CA.js

export default {

[LOCALES.FRENCH]: { ‘hello’: ‘Bonjour’, ‘userName’: ‘le nom d\’ utilisateur est {uname}’

}

};

translate.js

const translate = (id, value={}) => <FormattedMessage id={id} values={{…value}}/>

d. We are looking for the following output:

translate(‘hello’)  => Bonjour

translate(‘userName’, {‘uname’: ‘Sam’}) => le nom d’ utilisateur est Sam

Internationalization can be achieved in react application by using ‘React-intl’ with minimal development efforts for handling multiple languages.

MetaSys has developed custom React solutions for clients across various industries and geographies. If you have any questions on internationalization in your React projects, then please feel free to contact us. Happy coding!

To illustrate the advantages of this approach, have a look at the UI structure shown below.

Let’s say the functionality required is that when a user interacts with the big component, the application has to update the small component and the header. In other words, we need to sync the header and small component as well as manage the states of all the other components. Without a state management library such as the one provided by Redux, coding this implementation can easily become very complicated.

Using the state functionality in React allows only the use of local, component level states.

You can store the states using setState method, and fetch the stored state using state.[STATE_NAME]. However, these states are local, and only available within the class component in which it is declared.

To store the states at the application level, i.e. the global level, in order to access them from different components, we can use React-Redux.

Let’s see how React-Redux works

You will see three main elements in the Redux architecture – Store, Dispatch Actions and Reducers.

Store: holds the states at the application level, and allows any component to get data from the store in the form of Redux States.

Dispatch Action: a function of the Redux Store to trigger a state change.

Reducers: It handles the value change in Redux State.

How to configure React Redux in a React JS project –

The following packages are needed to be installed to configure  Redux in the project –

1. Redux: the core package of React Redux.
2. React-redux: needed for React bindings.
3. Redux-thunk: a middleware which allows you to call action creators, and which returns a function instead of the action object.

These dependencies can be installed by using the following NPM command –
“npm install redux react-redux redux-thunk –save”

After these dependencies are installed, a store can be created and initialized with data/null values as per the requirements. This can be done by creating the file store.js in the project.

First however, you need to create reducer.js to handle the next states. Below is the example of reducer.js to initialize the state. Here, it is just returning the initial value from the reducer.

Below is a slightly more complex example of the code in reducer.js to update the states based on the action executed from the component.

In the above example, it adds the data to the state upon the dispatch action (ADD_DATA). Now let’s create the action to dispatch. You can create a file with the name action.js, that contains the code shown below.

Once the action is created, now you can create a store and then connect the store to the application. You can create a file with the name store.js, that contains the code shown below.

To connect the store to the application, you will have to use the entry point. In the index.js (i.e. entry point of the app), import the store as shown below –

These are all the Redux configurations for an application. Refer the the image below to use it in your component –

React Redux can handle large amounts of data at the application level with cleaner components and is particularly useful for big applications.

Without redux, to transfer data from component 1 to component 5, you need to pass it through middle components. This increases the props for components and creates more complexity and the components are less clean.

Using React-Redux, you can get or set the data to the store from any of the components directly by mapping the redux states to component props. In this case, you do not need to pass props to the middle components. This allows for much cleaner components and increased clarity in the code.

If you are looking to build a mobile or web application using React technology, then please feel free to contact us.

React Hooks are functions that allow you to hook into React lifecycle and state features. They primarily serve as an alternative for classes. They can help in keeping your components clean and perform better. Hooks are a recent  addition in React version 16.8.0.

In this article, we are going to show you how to convert a React class into a functional component using the useState Hook.

Hooks don’t work inside classes because they let you use React without classes. We will use the built-in hooks instead of React lifecycle methods. Eg. useState, useEffect, useRef etc.

We are covering useState, useEffect, useRef React hooks in this article. useState() is used to replace the constructor functions and state declarations. While useEffect() is used to replace componentDidMount() and componentDidUpdate(). You can use useEffect as many times as you need to in single component. And the last one, useRef has another cool usage besides DOM refs, it is also a generic container whose current property is mutable, it also can hold any value similar to an instance property of a class.

Steps to convert a React class component into a functional component using React Hooks –

Step 1. Change ‘class ComponentName extends Component’ With ‘function ComponentName(props)‘

Step 2. Remove “this.” And “this.state” from the entire component.

Step 3. import React, { useState } from ‘react’

Step 4. Remove the constructor. Add its logic as shown above in the image for initializing the state variables with the help of useState hook.

Let’s understand conversion into useState, useEffect and useRef with examples –

• useState() Hook –

The parameter of the useState hook is the initial value of the state. This hook provides the array with two values – the first is the name of the state and the second is the function name which updates the value of that state.

Eg.

const [num, setNum] = useState(0); //declaration

setNum(10) //use

Here num is the state name, setCount is the function that you can use anywhere in the component to update that state.

Here are some examples of setting or initializing state variables for different data types –

//Set an Integer

const [num, setNum] = useState(0);

setNum(10);

//Set a String

const [name, setUsername] = useState(‘John’);

setUsername(‘Smith’);

//Set a Boolean

const [isValid, setIsValid] = useState(false);

setIsValid(true);

//Set and Array

const [items, setItems] = useState([]);

setItems([0,1,2,3,4]);

setItems([{id:0, color:”red”},{id:1, color:”green”},{id:2, color:”blue”}]);

//Set and Object

const [form, setValues] = useState({

id: 0,

firstName: ‘’,

lastName: ‘’,

subscribe: false

})

setValues({

…form,

firstName: ‘Jamie’,

subscribe: true

})

• Replace lifecycle methods (compentDidMount, componentWillUnmount,

 componentWillReceiveProps, componentDidUpdate) with useEffect

e.g.

const [items, setItems] = useState([]);

const [num, setNum] = useState(0);

1. compentDidMount

useEffect(()=>{

setItems(items);

}, [])   // Here empty array indicates don’t look for any updates

b.componentWillUnmount

useEffect(()=>{

return () => {console.log(‘unmounting the component’)}

},[])

c. componentDidUpdate/componentWillReceiveProps

This will get executed when your ‘num’ state variable and ‘id’ props will get updated.

useEffect(()=>{

if (!isEmpty(num))

{

console.log(‘num changed = ’,num);

setItems(items);

}

if(!isEmpty(props.id))

{

console.log(‘props.id changed = ’,props.id);

}

},[num, props.id])

• Use of useRef

const [num, setNum] = useState(0);

const prevNumRef = useRef();

useEffect(()=>{

prevNumRef.current = num;

})

const prevNum = prevNumRef.current;

return <h1>Current value : {num}, previous value = {prevNum}</h1>

Advantages

1.With React hooks, the component will be cleaner and easier to read (fewer lines of code). Hooks are easier to work with and to test.

2.It is easy to make code reusable. They don’t create another element in DOM like HOCs in React do.

3. useState – it allows to update different states with specific functions. The ability to move the state update logic as a separate hook.

Disadvantages

1.useEffect hook allows to merge three lifecycle methods such as componentDidMount, componentWillUnmount and componentDidUpdate into one and the issue with useEffect is the second parameters ,i.e. the array that we need to pass to define this behaviour. It is not explicit enough.

2.React Hooks are new additions to React. So to convert and test a complex class can be a time-consuming task initially .

3.Since it is relatively a new addition it may not be compatible with all third party libraries. But this is rapidly changing .

This is all about React Hooks in a nutshell. If you are looking to build any a mobile or web application using React technology, then please contact us.

Happy coding!