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To pass data from a parent component to a child in React, add named props to the child’s JSX tag, then read them from the child’s props object. Use quotes for string literals and curly braces for JavaScript values.
function Greeting({ name }) {
return <p>Hello, {name}</p>;
}
function App() {
return <Greeting name="Ada" />;
}Pass values on the child component’s JSX tag
A parent supplies a value by writing it as an attribute on the child component. Put a string literal in quotes; wrap JavaScript expressions—such as variables, numbers, objects, and function references—in curly braces. React’s guide to passing props and JSX curly-brace guide explain this syntax.
function App() {
const person = { name: "Ada" };
const handleClick = () => alert("Hello");
return (
<Avatar
person={person}
size={100}
label="Profile photo"
onClick={handleClick}
/>
);
}Here, label is a string, while person, size, and onClick are JavaScript expressions. An object literal can also be written with doubled braces, as in style={{ color: "blue" }}: the outer braces mark a JSX expression and the inner braces create a JavaScript object.
Read props in the child component
A function component receives one argument: a props object. You can destructure the values you need in the parameter, or accept the whole object and access its fields.
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function Avatar({ person, size }) {
return (
<img
src={person.imageUrl}
width={size}
height={size}
alt={person.name}
/>
);
}
// Equivalent access without destructuring:
function AvatarWithProps(props) {
return <img src={props.person.imageUrl} width={props.size} alt={props.person.name} />;
}Choose the style that makes the component easiest to read. The React props guide demonstrates both destructuring and access through the props object.
Set defaults for optional props
Use a JavaScript default value in the destructured parameter when a prop is optional:
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function Avatar({ size = 100 }) {
return <img width={size} height={size} alt="" />;
}This default applies when size is absent or its value is undefined. It does not replace an explicitly passed null or 0. Decide whether those values are valid for your component or require separate handling. The React props guide covers default prop values.
Pass nested content with children
When you place JSX between a component’s opening and closing tags, React passes that content as the children prop. A wrapper can render it without needing to know how the nested content is built.
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function Card({ children }) {
return <section className="card">{children}</section>;
}
function App() {
return (
<Card>
<h2>Account</h2>
<p>Your profile is ready.</p>
</Card>
);
}This composition pattern is useful for reusable wrappers such as cards, dialogs, and layout components. See React’s discussion of children.
Forward props selectively
You can forward an object of props with JSX spread syntax:
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function Parent({ childProps }) {
return <Child {...childProps} />;
}Spread is convenient when forwarding a known collection, but it can hide which values a child receives. When the list is short or the component boundary matters, name the props explicitly instead. Repeatedly forwarding many values through components that do not use them can also signal that the component structure or data path should be reconsidered. React advises using spread with restraint in its props guide.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Keep props read-only; put changing data in state
A child should not mutate values it receives through props. Props describe the values for a particular render; when data changes, the parent can render again with updated props. For interaction-driven changes, keep the changing data in state and pass the relevant value—and, when needed, a callback for requesting a change—to the child. React explains this render-time model in its props guide.
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Handle key and ref as special cases
key helps React identify elements in a list, and ref is handled specially by React; neither is forwarded as an ordinary prop. If the child also needs an identifier used as a key, pass it separately under a regular prop name:
results.map(result => (
<ResultRow key={result.id} id={result.id} result={result} />
))The child can read id and result, but should not expect to receive key. The React special props warning documents this behavior.
Choose props, children, or context for deeper data
Start with explicit props for parent-to-child communication: the data path is visible and easy to follow. Use children when composing nested UI or when a wrapper should not depend on the details of its contents. If many intermediate components only pass the same value along, consider restructuring the composition; if many descendants need shared data and explicit threading has become cumbersome, context may fit better. React cautions against adopting context solely because props pass through several levels; its guide to passing data deeply with context explains the trade-offs.
Class components
In a class component, read props through this.props rather than a function parameter:
class Greeting extends React.Component {
render() {
return <p>Hello, {this.props.name}</p>;
}
}React’s Component reference documents class components and recommends defining new components as functions.
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