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add initial previous value param to usePrevious hook #316

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add initial previous value param to usePrevious hook #316

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92c952d
add initial previous value param to usePrevious hook
wherehows Jul 4, 2024
34fb76f
add explanation about new parameter in the doc
wherehows Jul 4, 2024
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4 changes: 2 additions & 2 deletions index.js
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Expand Up @@ -1014,7 +1014,7 @@ export function usePreferredLanguage() {
);
}

export function usePrevious(value) {
export function usePrevious(value, initialPreviousValue) {
const [current, setCurrent] = React.useState(value);
const [previous, setPrevious] = React.useState(null);

Expand All @@ -1023,7 +1023,7 @@ export function usePrevious(value) {
setCurrent(value);
}

return previous;
return previous || initialPreviousValue;
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This works as default value, not the initial. Imagine calling usePrevious<number>(value, 1) with the value being: 1, 2, 0, 3. And we'll see 1, 1, 2, 1, right? It would be nice to have some tests confirming it works for some inputs...

}

export function useQueue(initialValue = []) {
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1 change: 1 addition & 0 deletions usehooks.com/src/content/hooks/usePrevious.mdx
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Expand Up @@ -26,6 +26,7 @@ import StaticCodeContainer from "../../components/StaticCodeContainer.astro";
| Name | Type | Description |
| -------- | ---- | -------------------------------------------------- |
| newValue | any | The new value to track and return the previous of. |
| initialValue | any | (Optional) The initial Previous Value. Default value is null.
</div>

### Return Value
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