Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsTo convert a React component without changing its behavior, make sure the project is configured for TypeScript, rename any file containing JSX to .tsx, then describe the component’s props and any values TypeScript cannot safely infer. You can do this one component at a time; the framework’s TypeScript setup determines the exact configuration and commands.
1. Check your project’s TypeScript setup
Start with the instructions for the framework your React project uses. Frameworks may already configure TypeScript and JSX; avoid replacing their settings with a generic setup. React’s TypeScript guide covers existing React projects and notes that React types are provided by @types/react and @types/react-dom. TypeScript also needs the appropriate DOM library support and JSX compiler setting.
If the project is still JavaScript, TypeScript’s JavaScript migration guide describes an incremental approach, including allowJs to let a TypeScript project accept JavaScript files. That can be useful when converting a larger codebase gradually; it is not required just to type one component. Use the build and type-check commands documented for your project.
2. Rename the component file
Change a file containing JSX from .js or .jsx to .tsx. The React documentation states: “Every file containing JSX must use the .tsx file extension.” A TypeScript file without JSX can use .ts.
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TypeScript’s JSX handbook also requires a jsx compiler option. JSX modes differ in whether JSX is preserved or transformed, so keep the mode expected by the project’s framework rather than choosing one arbitrarily.
3. Give the component’s props a type
Define the shape of the props object with an interface or a type alias, then annotate the component parameter. Mark a field optional only if callers are allowed to omit it. A default parameter is a natural fit for an optional prop:
type ButtonProps = {
title: string;
disabled?: boolean;
};
function Button({ title, disabled = false }: ButtonProps) {
return <button disabled={disabled}>{title}</button>;
}Here, title is required, while callers may omit disabled; the function uses false in that case. For a component with only a couple of straightforward fields, an inline type can be readable. As the contract grows, a named type or interface makes it easier to understand and reuse.
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After adding the type, check every place that renders the component. A compiler error at a caller often means the caller is missing a required prop or passing a value of the wrong shape; update the contract or caller to match how the component is actually meant to work.
4. Let TypeScript infer simple hook types
Hooks do not need annotations just because a component has been converted. For example, useState(false) gives TypeScript an initial boolean value from which to infer the state type.
Add an explicit type when the initial value does not communicate the intended shape or when state has meaningful alternatives. For example, if a value can be either a user object or null, represent both possibilities in its type instead of suppressing the resulting errors. Reducers with multiple actions are easier to check when actions are modeled as a discriminated union; that lets TypeScript distinguish each action by its identifying field.
5. Type event handlers at the element boundary
React’s types include event definitions, and JSX often gives an inline handler its event type from the element and prop where it appears. If a handler needs an explicit annotation, choose the event type for the actual element and handler rather than applying a broad type by default.
Keep the type aligned with the value the handler receives. If a callback is passed to another component, its expected signature is part of that component’s props contract; if it handles a DOM event directly, use the corresponding React event type.
6. Choose children and style types to match the API
Type these props only if they are part of the component’s public contract. For children, React.ReactNode allows a broad range of renderable values, while React.ReactElement is narrower and requires an element rather than a primitive such as a string. Use the broader or narrower type based on what the component actually accepts.
For an inline style prop, React.CSSProperties describes React’s style-object shape. It does not mean every component needs to expose a style prop; include one only when callers should be able to provide inline styles.
7. Handle React 19 component defaults and prop validation
For React 19, function-component propTypes checks have been removed from the React package, which silently ignores their use. React recommends TypeScript or another type-checking solution. Function components also no longer support defaultProps; use optional props and default values in the function parameters instead. Class components retain defaultProps. These changes are described in the React 19 Upgrade Guide.
The guide includes npx codemod@latest react/prop-types-typescript as a codemod option. Treat its changes as a starting point: review the edits in your repository and validate them with the project’s normal checks.
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8. Fix type errors without changing runtime behavior
Once the component is typed, resolve errors where the mismatch originates: adjust an incorrect caller, make a genuinely optional prop optional, or describe real state alternatives such as null. Avoid using broad any types to silence errors; that removes checks rather than explaining the component’s contract.
Keep the migration incremental if that suits the project. A single component can be converted and checked independently, while allowJs can support a wider migration that still includes JavaScript files. The component’s runtime logic need not be rewritten simply because its file and data contracts are now typed.
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