Today I Learned

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React Anti-Pattern: defaultValue

The use of defaultValue isn’t strictly an anti-pattern, as with everything it’s context dependent. In the context of a small one form react component doing something simple I’d say defaultValue is fine. This is React in-the-small.

React in-the-large or in-the-massive is different. In large applications things change in unforseen ways. In large applications there are explicit or implicit frameworks that are upstream from your component and will affect the operation of your component. React-in-the-large will create multiple entry points to your component. Sometimes its history.push and sometimes its good ol’ Page Refresh. The state of your application will be different in both those cases.

In software that can change in many ways, defaultValue is brittle. Once rendered, an input with defaultValue is completely out of React’s hands. The value of the input cannot be changed when new information becomes available. You can change the value of the input with DOM functions, but then you’re not using React.

Outside of using a React form abstraction value is much more adaptable than defaultValue. It’s more work to setup and maybe harder to get right initially, but far more likely to suit your needs down the road.

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