'React' must be in scope when using JSX react/react-in-jsx-scope
Tags: react, abotwrotethis
Published: 2023-04-10 17:02:02

If you're working with React and JSX, you may have come across an error message that says `react/react-in-jsx-scope`. This error can happen when you try to use JSX code without importing the React library first. In this blog post, we'll explain why you need to have 'React' in scope when using JSX and how to fix this error.

## What is JSX?

JSX stands for JavaScript XML, which is an extension to the JavaScript language. It allows you to write HTML-like syntax in your JavaScript code, which makes it easier to create and manipulate user interfaces. JSX code gets transpiled to regular JavaScript at build time, so it can be understood and executed by the browser.

Here's an example of JSX code:

```
const element = <h1>Hello, World!</h1>;
```

This code creates a new element that will render the text "Hello, World!" as a heading.

## Why do you need to have 'React' in scope when using JSX?

The React library provides a set of tools and functions that you can use to create and manipulate components. When you're working with JSX, you're actually using React to create those components, even if you're not aware of it. JSX code gets transpiled to a `React.createElement()` function call, which is a part of the React library.

However, for this transpilation to happen, React needs to be in scope. This means that React has to be present in the context of the file where you're using JSX. If React is not present, the transpilation will fail, and you'll see the `react/react-in-jsx-scope` error message.

## How to fix the 'React' must be in scope when using JSX error

If you're seeing the `react/react-in-jsx-scope` error, it means that you need to add an import statement for the React library at the top of your file. Here's an example of how to do this:

```
import React from 'react';

const element = <h1>Hello, World!</h1>;
```

This code imports the React library and assigns it to a variable called `React`. This variable then gets used in the JSX code to create the heading element.

Note that you don't actually need to use the `React` variable anywhere in your code. Just having it in scope is enough for JSX to work.

## Common mistakes to avoid

Here are some common mistakes that can result in the `react/react-in-jsx-scope` error:

### 1. Not importing the React library

If you forget to import the React library, you'll get the `react/react-in-jsx-scope` error. Make sure to add the import statement at the top of your file.

### 2. Using a different variable name

In the import statement, you need to use the name `React` to assign the library to a variable. If you use a different name, you'll get the `react/react-in-jsx-scope` error. For example, this won't work:

```
import MyReact from 'react';
```

You'll need to change it to:

```
import React from 'react';
```

### 3. Using JSX outside of a React component

JSX can only be used inside of a React component. If you try to use JSX outside of a component, you'll get the `react/react-in-jsx-scope` error. Make sure that your JSX code is inside a component's `render()` method.

## Conclusion

In this blog post, we've explained why you need to have 'React' in scope when using JSX and how to fix the `react/react-in-jsx-scope` error. Remember to import the React library at the top of your file and use the name `React` to assign it to a variable. If you do this, you'll be able to use JSX to create and manipulate components in your React app.