Conditional Rendering

Q: What is the best way to conditionally render a component?

Use a ternary {condition ? : } to choose between two elements, or {condition && } to show or hide one element. For complex multi-branch logic, use a variable or lookup object before the return.

Q: Why does 0 && Component render "0" on screen?

JavaScript's && operator returns the first falsy value. 0 is falsy but is a valid React child that renders as text. Use {count > 0 && } or a ternary instead.

Q: When should I use early return vs ternary?

Early return for guarding the entire component (loading, error, not-found states) Ternary for inline switches within the JSX tree Early returns are more readable when there are multiple guard conditions

Q: What is the lookup object pattern for conditional rendering?

Map state values to JSX elements using a Record:

Q: How do I preserve state when toggling between two views?

Render both and toggle visibility with CSS display: none Lift the state up to a parent component that persists across both views Use a shared state store like Zustand

Q: What is a discriminated union and how does it help conditional rendering?

A TypeScript union where each member has a literal status field. The switch or if on status narrows the type, so TypeScript knows which fields are available in each branch - eliminating undefined checks.

Q: When should I use CSS display:none vs conditional rendering?

Use display: none when you want to keep the component mounted and preserve its state (e.g., tab panels) Use conditional rendering when the hidden content is expensive to render, fetches data, or runs effects you want to stop

Q: How do I render nothing from a component?

Return null. This is cleaner than returning an empty Fragment <> and is the standard pattern for components that conditionally have no output.

Show, hide, or swap UI based on state, props, or computed values.

Recipe

Quick-reference recipe card - copy-paste ready.

// Ternary - pick between two elements
{isLoggedIn ? <Dashboard /> : <LoginForm />}
 
// Logical AND - show or nothing
{hasNotifications && <Badge count={notifications.length} />}
 
// Early return - bail out of the whole component
if (!user) return <Skeleton />;
return <Profile user={user} />;
 
// Extracted variable - readable when logic is complex
const content = status === "loading"
  ? <Spinner />
  : status === "error"
  ? <ErrorMessage />
  : <DataTable rows={data} />;
 
return <section>{content}</section>;

When to reach for this: Any time the UI changes based on a condition - loading states, auth gates, feature flags, empty states.

Working Example

"use client";
 
import { useState } from "react";
 
type Status = "idle" | "loading" | "success" | "error";
 
interface FetchResult {
  status: Status;
  data?: string[];
  error?: string;
}
 
export function FetchDemo() {
  const [result, setResult] = useState<FetchResult>({ status: "idle" });
 
  async function handleFetch() {
    setResult({ status: "loading" });
    try {
      // Simulate network request
      await new Promise(resolve => setTimeout(resolve, 1000));
      const success = Math.random() > 0.3;
      if (!success) throw new Error("Network timeout");
      setResult({
        status: "success",
        data: ["React", "Next.js", "TypeScript"],
      });
    } catch (err) {
      setResult({
        status: "error",
        error: err instanceof Error ? err.message : "Unknown error",
      });
    }
  }
 
  return (
    <div className="max-w-sm space-y-4 rounded border p-4">
      <button
        onClick={handleFetch}
        disabled={result.status === "loading"}
        className="rounded bg-blue-600 px-4 py-2 text-white disabled:opacity-50"
      >
        {result.status === "loading" ? "Fetching..." : "Fetch Data"}
      </button>
 
      {result.status === "idle" && (
        <p className="text-gray-500">Press the button to load data.</p>
      )}
 
      {result.status === "loading" && (
        <div className="animate-pulse rounded bg-gray-200 p-4">Loading...</div>
      )}
 
      {result.status === "error" && (
        <div className="rounded bg-red-50 p-3 text-red-700">
          <strong>Error:</strong> {result.error}
        </div>
      )}
 
      {result.status === "success" && result.data && (
        <ul className="list-inside list-disc">
          {result.data.map(item => (
            <li key={item}>{item}</li>
          ))}
        </ul>
      )}
    </div>
  );
}

What this demonstrates:

Discriminated union (Status) driving four distinct UI states
&& operator to render each state branch independently
Disabled button with conditional label text
Type narrowing - result.data is safely accessed only in the "success" branch

Deep Dive

How It Works

React renders whatever the component function returns - there's no special template syntax for conditionals
false, null, undefined, and true are valid JSX children that render nothing, which is why && and ternaries work
When a conditional flips and the component type at a position changes (e.g., <Spinner /> to <DataTable />), React unmounts the old tree and mounts a fresh one
When the component type stays the same but props change, React updates in place

Patterns Compared

Pattern	Best For	Example
Ternary `? :`	Choosing between two elements	`{ok ? <A /> : <B />}`
`&&`	Showing or hiding one element	`{show && <Modal />}`
Early return	Guarding the entire component	`if (!data) return null;`
Variable extraction	Complex multi-branch logic	`const ui = ...;`
Map/lookup object	Many discrete states	`statusMap[status]`

Lookup Object Pattern

const statusUI: Record<Status, React.ReactNode> = {
  idle: <p>Waiting...</p>,
  loading: <Spinner />,
  success: <DataTable />,
  error: <ErrorBanner />,
};
 
return <div>{statusUI[status]}</div>;

TypeScript Notes

// Discriminated unions make conditional rendering type-safe
type Result =
  | { status: "idle" }
  | { status: "loading" }
  | { status: "success"; data: string[] }
  | { status: "error"; error: string };
 
function Display({ result }: { result: Result }) {
  switch (result.status) {
    case "idle":
      return <p>Ready</p>;
    case "loading":
      return <Spinner />;
    case "success":
      // result.data is narrowed to string[] here
      return <List items={result.data} />;
    case "error":
      // result.error is narrowed to string here
      return <Alert message={result.error} />;
  }
}

Gotchas

0 && renders a literal 0 - {count && <Badge />} outputs 0 on screen when count is zero because 0 is a falsy but renderable value. Fix: Use {count > 0 && <Badge />} or a ternary.
Missing null return - A component that conditionally returns JSX but has no fallback return implicitly returns undefined, which works but triggers linting warnings. Fix: Explicitly return null for the empty case.
State reset on type change - Switching between <input type="text" /> and <textarea /> at the same tree position destroys state because they're different element types. Fix: If you need to preserve state, render both and toggle visibility with CSS, or lift state up.
Nested ternaries - {a ? b ? <X /> : <Y /> : <Z />} is hard to read and easy to misparse. Fix: Extract into a variable or use a switch/map pattern.

Alternatives

Alternative	Use When	Don't Use When
CSS `display: none`	You want to keep the component mounted and preserve its state (e.g., tab panels)	The hidden content is expensive to render or involves network requests
`<Suspense>` + lazy	Conditionally loading an entire code-split chunk	Simple show/hide within an already-loaded component
Route-based rendering	Different "pages" that each have their own URL	Toggle within a single view

Real-World Example

From a production Next.js 15 / React 19 SaaS application (SystemsArchitect.io).

// Production example: Banner display with multiple guard clauses
// File: src/components/banner/banner-display.tsx
export default function BannerDisplay({ location, className }: BannerDisplayProps) {
  const { banners, loading, error, fetchBanners } = useBannerStore();
  const locationBanners = banners[location] || [];
 
  useEffect(() => {
    fetchBanners(location);
  }, [location]);
 
  // Guard clause 1: loading with no cached data
  if (loading && locationBanners.length === 0) {
    return null;
  }
 
  // Guard clause 2: error state
  if (error) {
    return null;
  }
 
  // Guard clause 3: no banners for this location
  if (locationBanners.length === 0) {
    return null;
  }
 
  // Happy path: render banners
  return (
    <div className={cn('space-y-4', className)}>
      {locationBanners.map((banner) => (
        <div
          key={banner.id}
          className={cn(
            'rounded-md py-2 px-4 shadow-sm',
            getBorderClass(banner.borderStyle),
            'bg-zinc-50 dark:bg-zinc-900',
            banner.customStyles
          )}
        >
          {banner.content}
        </div>
      ))}
    </div>
  );
}

What this demonstrates in production:

Three early return null statements act as guard clauses, preventing rendering when nothing useful can be shown
loading && locationBanners.length === 0 means show nothing while loading the first time, but keep showing stale banners during a refresh
banners[location] || [] provides a safe fallback so .length never throws on undefined
The cn() utility (clsx + tailwind-merge) conditionally joins class names
Design decision: returning null instead of a skeleton prevents layout shift for optional UI like banners

FAQs

What is the best way to conditionally render a component?

Use a ternary {condition ? <A /> : <B />} to choose between two elements, or {condition && <A />} to show or hide one element. For complex multi-branch logic, use a variable or lookup object before the return.

Why does `0 && Component` render "0" on screen?

JavaScript's && operator returns the first falsy value. 0 is falsy but is a valid React child that renders as text. Use {count > 0 && <Component />} or a ternary instead.

When should I use early return vs ternary?

Early return for guarding the entire component (loading, error, not-found states)
Ternary for inline switches within the JSX tree
Early returns are more readable when there are multiple guard conditions

What is the lookup object pattern for conditional rendering?

Map state values to JSX elements using a Record:

const statusUI: Record<Status, React.ReactNode> = {
  idle: <p>Waiting...</p>,
  loading: <Spinner />,
  success: <DataTable />,
  error: <ErrorBanner />,
};
return <div>{statusUI[status]}</div>;

Does conditional rendering unmount and remount components?

Yes, if the component type at a tree position changes (e.g., <Spinner /> to <DataTable />), React unmounts the old component and mounts a new one, destroying all state. If only props change on the same component type, React updates in place.

How do I preserve state when toggling between two views?

Render both and toggle visibility with CSS display: none
Lift the state up to a parent component that persists across both views
Use a shared state store like Zustand

What is a discriminated union and how does it help conditional rendering?

A TypeScript union where each member has a literal status field. The switch or if on status narrows the type, so TypeScript knows which fields are available in each branch - eliminating undefined checks.

Is it bad to use nested ternaries?

Yes, they're hard to read. For more than two branches, extract the logic into a variable, use a switch statement, or use the lookup object pattern.

When should I use CSS display:none vs conditional rendering?

Use display: none when you want to keep the component mounted and preserve its state (e.g., tab panels)
Use conditional rendering when the hidden content is expensive to render, fetches data, or runs effects you want to stop

How do I render nothing from a component?

Return null. This is cleaner than returning an empty Fragment <></> and is the standard pattern for components that conditionally have no output.

Can I use switch statements in JSX?

Not directly inside JSX. Extract it to a variable or a helper function:

function getStatusIcon(status: Status) {
  switch (status) {
    case "success": return <CheckIcon />;
    case "error": return <XIcon />;
    default: return null;
  }
}
return <div>{getStatusIcon(status)}</div>;

JSX and TSX - expression slots where conditionals live
Lists and Keys - rendering dynamic collections
Components - structuring conditional branches as separate components

react.dev - official React docs (Learn + full API reference)
react.dev/reference - pure API reference (Hooks, built-in components, directives)
patterns.dev - React design/component patterns

Recipe

Quick-reference recipe card - copy-paste ready.

// Ternary - pick between two elements
{isLoggedIn ? <Dashboard /> : <LoginForm />}
 
// Logical AND - show or nothing
{hasNotifications && <Badge count={notifications.length} />}
 
// Early return - bail out of the whole component
if (!user) return <Skeleton />;
return <Profile user={user} />;
 
// Extracted variable - readable when logic is complex
const content = status === "loading"
  ? <Spinner />
  : status === "error"
  ? <ErrorMessage />
  : <DataTable rows={data} />;
 
return <section>{content}</section>;

When to reach for this: Any time the UI changes based on a condition - loading states, auth gates, feature flags, empty states.

Working Example

"use client";
 
import { useState } from "react";
 
type Status = "idle" | "loading" | "success" | "error";
 
interface FetchResult {
  status: Status;
  data?: string[];
  error?: string;
}
 
export function FetchDemo() {
  const [result, setResult] = useState<FetchResult>({ status: "idle" });
 
  async function handleFetch() {
    setResult({ status: "loading" });
    try {
      // Simulate network request
      await new Promise(resolve => setTimeout(resolve, 1000));
      const success = Math.random() > 0.3;
      if (!success) throw new Error("Network timeout");
      setResult({
        status: "success",
        data: ["React", "Next.js", "TypeScript"],
      });
    } catch (err) {
      setResult({
        status: "error",
        error: err instanceof Error ? err.message : "Unknown error",
      });
    }
  }
 
  return (
    <div className="max-w-sm space-y-4 rounded border p-4">
      <button
        onClick={handleFetch}
        disabled={result.status === "loading"}
        className="rounded bg-blue-600 px-4 py-2 text-white disabled:opacity-50"
      >
        {result.status === "loading" ? "Fetching..." : "Fetch Data"}
      </button>
 
      {result.status === "idle" && (
        <p className="text-gray-500">Press the button to load data.</p>
      )}
 
      {result.status === "loading" && (
        <div className="animate-pulse rounded bg-gray-200 p-4">Loading...</div>
      )}
 
      {result.status === "error" && (
        <div className="rounded bg-red-50 p-3 text-red-700">
          <strong>Error:</strong> {result.error}
        </div>
      )}
 
      {result.status === "success" && result.data && (
        <ul className="list-inside list-disc">
          {result.data.map(item => (
            <li key={item}>{item}</li>
          ))}
        </ul>
      )}
    </div>
  );
}

What this demonstrates:

Discriminated union (Status) driving four distinct UI states
&& operator to render each state branch independently
Disabled button with conditional label text
Type narrowing - result.data is safely accessed only in the "success" branch

Deep Dive

How It Works

React renders whatever the component function returns - there's no special template syntax for conditionals
false, null, undefined, and true are valid JSX children that render nothing, which is why && and ternaries work
When a conditional flips and the component type at a position changes (e.g., <Spinner /> to <DataTable />), React unmounts the old tree and mounts a fresh one
When the component type stays the same but props change, React updates in place

Patterns Compared

Pattern	Best For	Example
Ternary `? :`	Choosing between two elements	`{ok ? <A /> : <B />}`
`&&`	Showing or hiding one element	`{show && <Modal />}`
Early return	Guarding the entire component	`if (!data) return null;`
Variable extraction	Complex multi-branch logic	`const ui = ...;`
Map/lookup object	Many discrete states	`statusMap[status]`

Lookup Object Pattern

const statusUI: Record<Status, React.ReactNode> = {
  idle: <p>Waiting...</p>,
  loading: <Spinner />,
  success: <DataTable />,
  error: <ErrorBanner />,
};
 
return <div>{statusUI[status]}</div>;

TypeScript Notes

// Discriminated unions make conditional rendering type-safe
type Result =
  | { status: "idle" }
  | { status: "loading" }
  | { status: "success"; data: string[] }
  | { status: "error"; error: string };
 
function Display({ result }: { result: Result }) {
  switch (result.status) {
    case "idle":
      return <p>Ready</p>;
    case "loading":
      return <Spinner />;
    case "success":
      // result.data is narrowed to string[] here
      return <List items={result.data} />;
    case "error":
      // result.error is narrowed to string here
      return <Alert message={result.error} />;
  }
}

Gotchas

0 && renders a literal 0 - {count && <Badge />} outputs 0 on screen when count is zero because 0 is a falsy but renderable value. Fix: Use {count > 0 && <Badge />} or a ternary.
Missing null return - A component that conditionally returns JSX but has no fallback return implicitly returns undefined, which works but triggers linting warnings. Fix: Explicitly return null for the empty case.
State reset on type change - Switching between <input type="text" /> and <textarea /> at the same tree position destroys state because they're different element types. Fix: If you need to preserve state, render both and toggle visibility with CSS, or lift state up.
Nested ternaries - {a ? b ? <X /> : <Y /> : <Z />} is hard to read and easy to misparse. Fix: Extract into a variable or use a switch/map pattern.

Alternatives

Alternative	Use When	Don't Use When
CSS `display: none`	You want to keep the component mounted and preserve its state (e.g., tab panels)	The hidden content is expensive to render or involves network requests
`<Suspense>` + lazy	Conditionally loading an entire code-split chunk	Simple show/hide within an already-loaded component
Route-based rendering	Different "pages" that each have their own URL	Toggle within a single view

Real-World Example

From a production Next.js 15 / React 19 SaaS application (SystemsArchitect.io).

// Production example: Banner display with multiple guard clauses
// File: src/components/banner/banner-display.tsx
export default function BannerDisplay({ location, className }: BannerDisplayProps) {
  const { banners, loading, error, fetchBanners } = useBannerStore();
  const locationBanners = banners[location] || [];
 
  useEffect(() => {
    fetchBanners(location);
  }, [location]);
 
  // Guard clause 1: loading with no cached data
  if (loading && locationBanners.length === 0) {
    return null;
  }
 
  // Guard clause 2: error state
  if (error) {
    return null;
  }
 
  // Guard clause 3: no banners for this location
  if (locationBanners.length === 0) {
    return null;
  }
 
  // Happy path: render banners
  return (
    <div className={cn('space-y-4', className)}>
      {locationBanners.map((banner) => (
        <div
          key={banner.id}
          className={cn(
            'rounded-md py-2 px-4 shadow-sm',
            getBorderClass(banner.borderStyle),
            'bg-zinc-50 dark:bg-zinc-900',
            banner.customStyles
          )}
        >
          {banner.content}
        </div>
      ))}
    </div>
  );
}

What this demonstrates in production:

Three early return null statements act as guard clauses, preventing rendering when nothing useful can be shown
loading && locationBanners.length === 0 means show nothing while loading the first time, but keep showing stale banners during a refresh
banners[location] || [] provides a safe fallback so .length never throws on undefined
The cn() utility (clsx + tailwind-merge) conditionally joins class names
Design decision: returning null instead of a skeleton prevents layout shift for optional UI like banners

FAQs

What is the best way to conditionally render a component?

Why does `0 && Component` render "0" on screen?

JavaScript's && operator returns the first falsy value. 0 is falsy but is a valid React child that renders as text. Use {count > 0 && <Component />} or a ternary instead.

When should I use early return vs ternary?

Early return for guarding the entire component (loading, error, not-found states)
Ternary for inline switches within the JSX tree
Early returns are more readable when there are multiple guard conditions

What is the lookup object pattern for conditional rendering?

Map state values to JSX elements using a Record:

const statusUI: Record<Status, React.ReactNode> = {
  idle: <p>Waiting...</p>,
  loading: <Spinner />,
  success: <DataTable />,
  error: <ErrorBanner />,
};
return <div>{statusUI[status]}</div>;

Does conditional rendering unmount and remount components?

How do I preserve state when toggling between two views?

Render both and toggle visibility with CSS display: none
Lift the state up to a parent component that persists across both views
Use a shared state store like Zustand

What is a discriminated union and how does it help conditional rendering?

Is it bad to use nested ternaries?

Yes, they're hard to read. For more than two branches, extract the logic into a variable, use a switch statement, or use the lookup object pattern.

When should I use CSS display:none vs conditional rendering?

Use display: none when you want to keep the component mounted and preserve its state (e.g., tab panels)
Use conditional rendering when the hidden content is expensive to render, fetches data, or runs effects you want to stop

How do I render nothing from a component?

Return null. This is cleaner than returning an empty Fragment <></> and is the standard pattern for components that conditionally have no output.

Can I use switch statements in JSX?

Not directly inside JSX. Extract it to a variable or a helper function:

function getStatusIcon(status: Status) {
  switch (status) {
    case "success": return <CheckIcon />;
    case "error": return <XIcon />;
    default: return null;
  }
}
return <div>{getStatusIcon(status)}</div>;

JSX and TSX - expression slots where conditionals live
Lists and Keys - rendering dynamic collections
Components - structuring conditional branches as separate components

react.dev - official React docs (Learn + full API reference)
react.dev/reference - pure API reference (Hooks, built-in components, directives)
patterns.dev - React design/component patterns

Conditional Rendering

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Conditional Rendering