JavaScript Why use spread operator in this react program? What does it do?

[shivajikobardan]

TL;DR Summary

spread operator in react js.

Code for this is here:

https://codesandbox.io/s/floral-frog-7zfon3

I got the general idea of program flow in this case.

First user clicks a button, then function gets called, that function in turn updates the state from initial [] state to [{id:1,value:0.12232}]. Now the array map accesses the value and displays in a list.

But I don't understand why did we use spread operator there. If I remove spread operator, I can see the difference, but I'm not understanding what spread operator is doing here enough to apply the concept of spread operator in other projects.

I have learnt about spread operator from MDN docs already.

 

[jedishrfu]

The spread operator is actually a part of javascript ES6 not react.js

However, the spread operator in React.js is used to spread an array of values or the properties of an object into a new array or object. It is represented by three dots (...).

Here is an example of how the spread operator can be used in React.js to create a new array that combines two existing arrays:

const array1 = [1, 2, 3];
const array2 = [4, 5, 6];

const combinedArray = [...array1, ...array2];
// combinedArray is now [1, 2, 3, 4, 5, 6]

The spread operator can also be used to spread the properties of an object into a new object:

const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4 };

const combinedObject = { ...obj1, ...obj2 };
// combinedObject is now { a: 1, b: 2, c: 3, d: 4 }

The spread operator is a useful tool for creating new arrays or objects that are based on existing ones, without modifying the original arrays or objects. It is often used in React.js to pass props from a parent component to a child component or to make a shallow copy of an object or array.

References:

• "Spread syntax - JavaScript | MDN" (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax)
• "React - JSX in Depth" (https://reactjs.org/docs/jsx-in-depth.html)
• "React - React Fundamentals" (https://reactjs.org/docs/getting-started.html)

MENTOR Note: I got most of this answer by asking ChatGPT about the spread operator for react.js and asking it to cite references

My citation reference is::

 

[shivajikobardan]

thank you