This article aims to provide a clear understanding of the distinctions between JSX.Element, ReactNode, and ReactElement in TypeScript when working with React.
JSX.Element is an interface that represents the expected props in a React component.
ReactNode is a versatile type that encompasses various renderable elements in React, such as text, numbers, booleans, null, undefined, portals, ReactElements, or arrays of ReactNodes.
ReactElement, on the other hand, refers to an object with a type and props, which can be created using JSX or React.createElement.
It is important to differentiate JSX.Element from ReactElement, as the former is a global namespace defined by the React library, while the latter serves as the return type for function components and is employed to generate elements in React.
Notably, although React.FC (FunctionComponent) type may also be used for function components, it is not advised due to certain quirks and is no longer included in Create React App templates.
This article will explore the type definitions, differences, and appropriate usage scenarios for JSX.Element, ReactNode, and ReactElement.
JSX.Element vs ReactNode vs ReactElement:
The distinction between JSX.Element, ReactNode, and ReactElement is important as they represent different concepts in React.
JSX.Element represents the expected props in a React component. It is a global namespace set by the React library. JSX.Element has a generic type for props and type being any.
ReactElement, on the other hand, is an object with a type and props created using JSX or React.createElement. It is used as the return type for function components. ReactElement is similar to JSX.Element in that it also has a generic type for props and type being any.
ReactNode is used as the return type for the render() method in class components. It represents anything that React can render. ReactNode can represent a wider range of content that React can render compared to JSX.Element and ReactElement.
In summary, JSX.Element represents the expected props in a React component, ReactElement is used as the return type for function components, and ReactNode represents anything that React can render. These distinctions are important for understanding and working with React components effectively.
Type Definitions
Type definitions for JSX.Element, ReactNode, and ReactElement are essential in TypeScript for accurately representing and manipulating various types of content that can be rendered in React components.
JSX.Element serves as an interface for the expected props in a React component, while ReactNode represents any type of content that React can render.
On the other hand, ReactElement is an object that consists of a type and props, which can be created using JSX or React.createElement. Both JSX.Element and ReactElement have a generic type for props and type, allowing flexibility in their usage.
ReactNode is typically used as the return type for the render() method in class components, while function components return ReactElement. However, the distinction in return types is due to historical reasons and backward compatibility.
In rare cases, type assertions or Fragments may be used as workarounds, and React 18 introduces ReactFragment and IterableReactNode as replacements for ReactNode.
Differences and Usage
Differences in return types for class and function components arise due to historical reasons and the need for backwards compatibility. Ideally, both class and function components would have the same valid return types, including ReactElement, Array
This distinction is a result of the evolution of React and the introduction of JSX. JSX.Element is a global namespace that represents the expected props in a React component, while ReactElement is an object with a type and props, created using JSX or React.createElement.
To handle null values, ReactElement | null can be used as the type, or TypeScript can infer the type. In edge cases, type assertions or Fragments can be used as workarounds.
React.FC (FunctionComponent) type can also be used for function components, but it is advised to avoid it due to quirks and lack of inclusion in Create React App templates.
