How do you solve React must be in scope when using JSX React React in JSX scope?

The answer to this question was “yes” in the past, but with React 17 release, the current answer is “no”.

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Rule Details
When Not To Use It
What does React must be in scope when using JSX?
Is it possible to loop inside JSX if not how can we write loop in JSX?
Is it mandatory to use JSX in React?
How does JSX work in React?

JSX transform:

Browsers don’t understand JSX out of the box, so most React users rely on a compiler like Babel to transform JSX code into regular JavaScript. Many preconfigured toolkits like Create React App or Next.js also include a JSX transform under the hood. With React 17, JSX transform has been improved; here’re the benefits of the new JSX transform:

With the new transform, you can use JSX without importing React.
Depending on your setup, its compiled output may slightly improve the bundle size.
It will enable future improvements that reduce the number of concepts you need to learn React.

What’s Different in the New transform?

When you use JSX, the compiler transforms it into React function calls that the browser can understand. The old JSX transform turned JSX into React.createElement(...) calls.

For example, let’s say your source code looks like this:

Under the hood, the old JSX transform turns it into regular JavaScript:

However, this is not perfect:

Because JSX was compiled into React.createElement, React needed to be in scope if you used JSX.
There are some performance improvements and simplifications that React.createElement does not allow.

To solve these issues, React 17 introduces two new entry points to the React package that are intended to only be used by compilers like Babel and TypeScript. Instead of transforming JSX to React.createElement, the new JSX transform automatically imports special functions from those new entry points in the React package and calls them.

Let’s say that your source code looks like this:

This is what the new JSX transform compiles it to:

Note how our original code did not need to import React to use JSX anymore! (But we would still need to import React in order to use Hooks or other exports that React provides.)

This change is fully compatible with all of the existing JSX code, so you won’t have to change your components.

If you are using the @jsx pragma this rule will check the designated variable and not the

/** @jsx Foo.bar */
var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

0 one.

Rule Details

Examples of incorrect code for this rule:

var Hello = <div>Hello {this.props.name}</div>;

/** @jsx Foo.bar */
var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

Examples of correct code for this rule:

import React from 'react';

var Hello = <div>Hello {this.props.name}</div>;

var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

/** @jsx Foo.bar */
var Foo = require('foo');

var Hello = <div>Hello {this.props.name}</div>;

When Not To Use It

If you are not using JSX, or if you are setting

/** @jsx Foo.bar */
var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

0 as a global variable.

If you are using the new JSX transform from React 17, you should disable this rule by extending

/** @jsx Foo.bar */
var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

3 in your eslint config (add

/** @jsx Foo.bar */
var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

4 to

/** @jsx Foo.bar */
var React = require('react');

var Hello = <div>Hello {this.props.name}</div>;

5).

What does React must be in scope when using JSX?

React Must Be in Scope Since JSX compiles into calls to React.createElement , the React library must also always be in scope from your JSX code. If you don't use a JavaScript bundler and loaded React from a <script> tag, it is already in scope as the React global.

Is it possible to loop inside JSX if not how can we write loop in JSX?

Using the Array map function is a very common way to loop through an Array of elements and create components according to them in React. This is a great way to do a loop which is a pretty efficient and is a tidy way to do your loops in JSX. It's not the only way to do it, but the preferred way.

Is it mandatory to use JSX in React?

JSX is not a requirement for using React. Using React without JSX is especially convenient when you don't want to set up compilation in your build environment. Each JSX element is just syntactic sugar for calling React.

How does JSX work in React?

JSX allows us to write HTML elements in JavaScript and place them in the DOM without any createElement() and/or appendChild() methods. JSX converts HTML tags into react elements. You are not required to use JSX, but JSX makes it easier to write React applications.