How to pass props to a child component?
The most common way for a parent component to pass data to a child component is through props. The basic method is to directly pass props, for example, in the parent component
In React, the most common way for the parent component to pass data to the child component is through props. It is actually not complicated to operate, but there are several key points that need to be paid attention to, especially when you first learn it, it is easy to get confused.
Basic method: directly transmit props
If the parent component wants to pass data to the child component, you only need to add the prop name and value you need in the place where the child component is used, just like writing HTML attributes.
For example, if you have a UserCard component, you want to pass a username from the parent component:
// <UserCard name="Alice" /> in the parent component
Then in the subcomponent, use the function parameters to receive these props:
function UserCard(props) {
return <div>{props.name}</div>;
}Or if you are using deconstruction, you can also write it like this:
function UserCard({ name }) {
return <div>{name}</div>;
}This method is suitable for passing basic types such as strings, numbers, and boolean values, and is also suitable for passing objects and functions.
Passing functions is also a common requirement
Sometimes you not only want to pass data, but also want the child component to "notify" what happened to the parent component. At this time, you can pass a function as a prop.
For example, if you have a button in the child component, you should tell the parent component after clicking:
// Parent component function handleChildClick() {
console.log("Subcomponent triggered");
}
<ChildComponent onAction={handleChildClick} />Then call this function in the child component:
function ChildComponent({ onAction }) {
Return (
<button onClick={onAction}>
Click me to notify the parent component</button>
);
}This is very common in scenarios where there are many forms and interactions, such as notifying the parent component of the update status when the input box changes.
Be careful to avoid unnecessary re-rendering
Although it is convenient to pass props, if the object or function you pass is a new reference every time, it may cause unnecessary re-rendering of the child components. Especially for components that are more sensitive to optimization performance, the following points can be considered:
- Use
useCallbackto keep function references stable - Use
useMemoorReact.memoto optimize the object or component itself passed into the child component
For example, if a new function is created to the child component every time the parent component renders, even if the content of props does not change, the child component will be re-rendered if the reference changes. You can wrap it with useCallback :
const handleClick = useCallback(() => {
// Processing logic}, []);Then pass it to the subcomponent, so the reference will be stable.
Basically that's it. Props is one of the most basic operations in React development. It looks simple, but after a thorough understanding can you write a more efficient component structure.
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