React Spread

React Spread
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What is the meaning of spread operator (…) in Reactjs?
Difficulty Level :
Medium Last Updated :
23 Dec, 2020
import React, { Component } from 'react' ;
// Details is a component in same folder
class App extends React.Component {
        { /* Details component which accepts props */ }

import React, { Component } from 'react' ;
class Details extends React.Component {
    // To extract values in variables sent by parent component
    const { name, age } = { ... this .props };

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Got It !
The three dots syntax (…) is part of ES6 and not React itself and it’s used by two operators i.e. the Spread and Rest operators. The Spread operator lets you expand an iterable like an object, string, or array into its elements while the Rest operator does the inverse by reducing a set of elements into one array.
The spread operator is very useful when you want to make an exact copy of an existing array, you can use the spread operator to accomplish this quickly.
Step 1: Create a React application using the following command:
Step 2: After creating your project folder i.e. foldername , move to it using the following command:
Step to Run Application: Run the application using the following command from the root directory of the project:
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React has quickly become one of DMC’s favorite tools for web front-end development due to its component-based structure and growing adoption. However, between the JSX syntax, component lifecycle, and state management, learning to use React effectively sometimes feels like learning a language in and of itself.

JavaScript’s spread operator sees a lot of use in DMC’s React applications due to its concision and versatility. Here are 5 of our favorite uses of the spread operator (…) in a React application.

Probably the most common usage of the spread operator in a React app is in passing props down to a child component. So long as the object you’re spreading includes all the properties the child component requires, the child component will use those and ignore the extraneous ones.

This allows for much more concise code than breaking out each property that the child inherits from the parent. Note: we use Typescript in our applications, and these examples will use it as well for clarity.
If you have multiple component instances with some attributes in common, and others which differ, it can be helpful to pull them out into one object which is referenced by all instances. For example, instead of the following:
You can instead abstract the common props:
Similarly, you can map a function which generates an instance of the component using these common props over an array of the unique elements (shown in example 4), which is preferable for longer or dynamic element lists.

Leaving our button for a moment, another place where we frequently use the spread operator is in functions to handle change events for forms. We typically use the same function to handle changes for all fields in a form, to minimize code repetition.

The following syntax allows setting a property in the state with a dynamic key name while maintaining the other properties previously in the state:
As a note, this pattern is not necessary if using React without using Typescript. This is also a good point to emphasize the importance of order when using the spread operator. I like to think of the spread operator as literally spreading out (in order) the items in an object or list.

If you’re trying to overwrite an existing property, as I am in this case, it’s important to make sure it’s after the spread operator, or the existing property will overwrite your new value!

The spread operator can also be used working with arrays, which can be very useful in a React application. One situation we encounter frequently is adding an element to an array which is subsequently mapped and rendered. Doing so with the spread operator is simpler and cleaner than doing so with Javascript’s push() or concat().

For example, if our button list always needs to include a cancel button, we could do the following:
Our final favorite use of the spread operator is to strip properties from an existing object to make a new object without setting properties individually. We’ve found this most useful when making calls to an API, when we want to be careful to send only the data we intend.

Specifying all the properties we want on the new object can be quite verbose:
Instead, by using destructuring with the rest syntax, we can specify the properties we want to exclude from the new object.

Javascript’s spread operator is a powerful tool to minimize boilerplate in a React application and make it easy to read and maintain in addition to its natural performance benefits.

If you’re interested in working with DMC on a React application, feel free to contact us .
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ReactJS: How to Use the Spread Operator (...)
Amongst the many scary operations in programming, the Spread operator can be difficult to understand as a newbie trying to saddle the deep waters of software development. Especially, if you do not have a background in computer science.
In this post, you will learn what the Spread operator is, and its uses in JavaScript and ReactJS. So you can start enjoying your learning journey as a software developer.
The Spread operator is a Javascript operator that can be used when all elements from an object or array need to be included in a list of some kind. It offers you access to the internals of an iterable.
The word “iterable” refers to a group of data types in computer science. Arrays, object literals, and strings, to be specific.
In a simpler term, a Spread operator allows us to quickly copy all or part of an existing array or object into another array or object. It is an ES6 syntax represented with a three-dot (…).
The Rest operator, like the Spread operator, adopts the three-dot syntax. In contrast to the Spread operator, the Rest operator works in the other direction. i.e, While the Spread operator expands an iterable into its elements, the Rest operator reduces a set of elements to a single array.
Below are the different ways you can apply the JavaScript Spread operator.
1. Concatenating iterable Objects and Arrays: There are different ways to concatenate or merge objects in javaScript. However, the Spread operator is the easiest way to merge two or more objects into a new one that contains the properties of the merged objects.
From the above example, the existing objects in bucketList and wishList have been merged into the new object in myDreams with the Spread operator.
In the example above we can see that the spread operator unpacks the elements of the items array.
3. Constructing Array literals: When you need to add a new item to a local data store or display all previously stored items along with a new addition, the spread operator comes in handy.
4. On strings: The Spread operator when used on strings, separates each character of the string into individual characters.
5. Passing Props in React: Passing props down to a child component is perhaps the most common use of the spread operator in a React app. If the object you’re spreading contains all of the properties that the child component requires, the child component will use those and ignore the rest.
Instead of splitting out each attribute that the kid inherits from the parent, this allows for considerably more simple code.
In the example above, both components are equivalent.
In conclusion, the JavaScript Spread operator is a very simple and powerful tool that will save you a few lines of code and enhance maintainability in a React application.
I am a web developer who loves to share and help others trying to get in web development.
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Daniel Yerimah This is gold! Its an excellent resource you've put together. You should share more of these often. Thumbs up mate!
Thank you so much, buddy...I really appreciate this.
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