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Rendering Conditional Render

Source: .agents/references/coding-standard/vercel-react-best-practices/rules/rendering-conditional-render.md

Metadata​

  • title: Use Explicit Conditional Rendering
  • impact: LOW
  • impactDescription: prevents rendering 0 or NaN
  • tags: rendering, conditional, jsx, falsy-values

Content​

Use Explicit Conditional Rendering​

Use explicit ternary operators (? :) instead of && for conditional rendering when the condition can be 0, NaN, or other falsy values that render.

Incorrect (renders "0" when count is 0):

function Badge({ count }: { count: number }) {
  return (
    <div>
      {count && <span className="badge">{count}</span>}
    </div>
  )
}

// When count = 0, renders: <div>0</div>
// When count = 5, renders: <div><span class="badge">5</span></div>

Correct (renders nothing when count is 0):

function Badge({ count }: { count: number }) {
  return (
    <div>
      {count > 0 ? <span className="badge">{count}</span> : null}
    </div>
  )
}

// When count = 0, renders: <div></div>
// When count = 5, renders: <div><span class="badge">5</span></div>