TypeScript with React: Mastering the 'children' Prop

Photo by Minhaz on Unsplash

In the realm of TypeScript, leveraging its type definitions and inferences becomes pivotal for robust code. When amalgamating TypeScript with frameworks like ReactJS, harnessing the full potential of TypeScript becomes a crucial aspiration.

One ubiquitous prop across ReactJS components is children. However, in each project or use-case several questions arise:

• Should developers define it at the project/app level?
• Can we specify certain primitives or specific JSX elements?
• What are the best practices?

Unveiling ReactJS’s Essential Types

Fortunately, ReactJS’s documentation houses a section on Useful Types, highlighting the DefinitelyTyped project where a type declaration resides ready for implementation in your code.

type PropsWithChildren<P = unknown> = P & { children?: ReactNode | undefined };

The PropsWithChildren type definition rely on ReactNode and uses Generic type definition based on some passed type. Passing specific component type such as ComponentProps result in a type that extends the passed ComponentProps type with the children prop.

Implementation

For instance, consider a straightforward component with only two props and the children prop:

interface ComponentProps {
    age: number;
    name: string;
}

const Component = ({ age, name, children }: PropsWithChildren<ComponentProps>) {
    /* ... */
}

Precision in Value Assertion

According to official ReactJS documentation, while it’s impossible to define specific JSX elements directly, limiting the children prop solely to JSX elements is achievable using ReactElement instead of ReactNode.

ReactNode is the most broad type definition that accepts all options: ReactElement and JavaScript primitive types such as numbers and strings.

Usage

interface UserComponentProps {
    age: number;
    name: string;
    children: ReactNode; // will accept all possible values
}

const UserComponent = ({ age, name, children }: UserComponentProps) {
    /* ... */
}

interface UserSpecificComponentProps {
    age: number;
    name: string;
    children: ReactElement; // will accept only JSX elements
}

const UserSpecificComponent = ({ age, name, children }: UserSpecificComponentProps) {
    /* ... */
}

Final Thoughts

Mastering the children prop in ReactJS with TypeScript is one important step to understand how both technologies can work seamlessly together.

Whether you have questions, insights to share, or want to explore more frontend wonders, let’s connect and continue this conversation! Reach out to me on LinkedIn or X/Twitter.