React Tip: Unique IDs in API Data

🔖React Tip: When Your “id” Isn’t Really Unique Recently ran into an interesting issue while working with API data in React. I was rendering a table and opening a popup when clicking on a cell - seemed simple enough. The API response looked like this: [ { id: "101", name: "101", age: 25 }, { id: "102", name: "102", age: 27 } ] Both `id` and `name` had the same values, and I didn’t think much of it at first. But when I opened the popup from the ID cell, it sometimes showed the wrong record or didn’t update at all. Here’s what the code looked like: {data.map((item) => ( <tr key={item.id}> <td onClick={() => openPopup(item.id)}>{item.id}</td> <td>{item.name}</td> </tr> ))} ⁉️The problem? React uses the `key` prop to identify DOM elements. If multiple rows share the same key value, React may reuse elements incorrectly. Also, since the popup logic was using `id` for lookup, it always returned the first matching record. Here’s the safer version: {data.map((item, index) => ( <tr key={index}> <td onClick={() => openPopup(item)}>{item.id}</td> <td>{item.name}</td> </tr> ))} And the popup handler: const openPopup = (rowData) => setSelected(rowData); 🧠Lesson learned: even something as small as duplicate `id` fields can cause surprising bugs in React tables. Always make sure your keys are unique and your popup or event logic doesn’t rely on repeated identifiers. #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #ReactTips

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