Conditional rendering allows components to decide what to display based on certain conditions. React provides several ways to implement conditional rendering, making it easy to display different UI elements based on the state or props of a component.

1. Using if-else Statements

You can use standard JavaScript if-else statements for conditional rendering within a component. Typically, you would do this outside of the JSX return statement, such as within the render function or directly before the return.

Example: Using if-else

function Greeting({ isLoggedIn }) {
    let message;
    
    if (isLoggedIn) {
        message = <h1>Welcome Back!</h1>;
    } else {
        message = <h1>Please Sign In</h1>;
    }

    return <div>{message}</div>;
}

In this example, if-else is used to set the value of message based on the isLoggedIn prop, which is then rendered inside the component.

2. Using Ternary Operators

A ternary operator is a shorthand for if-else and is commonly used for inline conditional rendering within JSX. It has the following syntax:

condition ? expression_if_true : expression_if_false;

Example: Using Ternary Operator

function Greeting({ isLoggedIn }) {
    return (
        <div>
            {isLoggedIn ? <h1>Welcome Back!</h1> : <h1>Please Sign In</h1>}
        </div>
    );
}

In this example, if isLoggedIn is true, “Welcome Back!” is rendered; otherwise, “Please Sign In” is shown. Ternary operators are great for simple conditions.

3. Using && (Logical AND) Operator

The && (logical AND) operator can be used for conditional rendering when you want to display something only if a condition is true. This is useful for scenarios where you only want to render an element when a certain condition holds.

Example: Using && Operator

function Notification({ message }) {
    return (
        <div>
            {message && <p>{message}</p>}
        </div>
    );
}

In this example, the paragraph will only be rendered if message is truthy. If message is null or undefined, nothing will be displayed.

4. Conditional Rendering Based on Multiple Conditions

You can also combine if-else, ternary operators, and && logic for more complex conditions.

Example: Multiple Conditions

function UserStatus({ user }) {
    return (
        <div>
            {user ? (
                user.isAdmin ? (
                    <h1>Welcome, Admin!</h1>
                ) : (
                    <h1>Welcome, {user.name}!</h1>
                )
            ) : (
                <h1>Please log in</h1>
            )}
        </div>
    );
}

In this example, multiple conditions are checked using nested ternary operators to display different messages based on whether the user is logged in and whether they are an admin.

Summary of Conditional Rendering Methods

Best Practices

• Use ternary operators for simple conditions, especially within JSX.
• Use && for conditional rendering when you only want to render an element when a condition is true.
• For more complex logic, prefer if-else statements outside of JSX.

By using these techniques, you can conditionally render content in React based on various states, props, or conditions, enabling dynamic and interactive user interfaces.

References

• https://www.w3schools.com/react/react_conditional_rendering.asp
• https://legacy.reactjs.org/docs/conditional-rendering.html