Key Prop

In React, the key prop is a special attribute used when rendering dynamic lists of elements. It gives each element a stable identity, which helps React efficiently update the UI by tracking which items have changed, been added, or been removed during re-renders.

Without keys, React relies on index positions, which can lead to unexpected behavior, especially in cases of reordering or dynamic data changes.

Why Keys Matter

• Performance: React uses keys to optimize the diffing algorithm, minimizing DOM updates.

• Correctness: Ensures proper component state preservation and rendering order.

• Avoids UI bugs: Prevents mismatches between UI elements and their underlying data.

Example:

const items = ['Apple', 'Banana', 'Cherry'];
return (
  <ul>
    {items.map((item) => (
      <li key={item}>{item}</li>
    ))}
  </ul>
);

Best Practices:

• Use a unique, stable ID if available (e.g., item.id from a database).

• Avoid using array indexes as keys if the list can change order or have insertions/removals.

• Keys should be consistent between renders to avoid unnecessary re-renders.

Common Mistake:

// Using index as key

items.map((item, index) => <li key={index}>{item}</li>);

This can cause bugs if items are reordered or removed.

Why It Matters

React’s reconciliation process depends heavily on keys for list rendering. Using keys correctly leads to more efficient, bug-free, and predictable UI updates—especially in complex, interactive apps.

What is Superflex.ai?

We’ve all seen great designs lose their edge during development. Superflex solves that by generating real, usable React components directly from your Figma files. It respects your design system, keeps your UI logic clean, and helps developers stay true to the original vision—without extra interpretation or cleanup.