Conditional Rendering

The If component is a utility component for conditional rendering in React applications. It provides a clean, declarative way to render content based on a condition, with support for fallback content.

Features

• Conditional rendering based on various types of conditions
• Support for render props pattern
• Optional fallback content
• Memoized for performance optimization

Usage

import { If } from '@kit/ui/if';
 
function MyComponent({ isLoggedIn, user }) {
  return (
    <If condition={isLoggedIn} fallback={<LoginPrompt />}>
      {(value) => <WelcomeMessage user={user} />}
    </If>
  );
}

Props

The If component accepts the following props:

• condition: Condition<Value> (required): The condition to evaluate. Can be any value, where falsy values (false, null, undefined, 0, '') are considered false.
• children: React.ReactNode | ((value: Value) => React.ReactNode) (required): The content to render when the condition is truthy. Can be a React node or a function (render prop).
• fallback?: React.ReactNode (optional): Content to render when the condition is falsy.

Types

type Condition<Value = unknown> = Value | false | null | undefined | 0 | '';

Examples

Basic usage

<If condition={isLoading}>
  <LoadingSpinner />
</If>

With fallback

<If condition={hasData} fallback={<NoDataMessage />}>
  <DataDisplay data={data} />
</If>

Using render props

<If condition={user}>
  {(user) => <UserProfile username={user.name} />}
</If>

Performance

The If component uses useMemo to optimize performance by memoizing the rendered output. This means it will only re-render when the condition, children, or fallback props change.

Best Practices

1. Use the If component for simple conditional rendering to improve readability.
2. Leverage the render props pattern when you need to use the condition's value in the rendered content.
3. Provide a fallback for better user experience when the condition is false.
4. Remember that the condition is re-evaluated on every render, so keep it simple to avoid unnecessary computations.

Typescript Support

The If component is fully typed and supports generic types for the condition value. This allows for type-safe usage of the render props pattern:

<If<User> condition={user}>
  {(user) => <UserProfile name={user.name} email={user.email} />}
</If>

The If component provides a clean and efficient way to handle conditional rendering in React applications, improving code readability and maintainability.