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snippets/unwind.md

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+---
+title: Unwind object
+tags: object
+expertise: intermediate
+firstSeen: 2022-04-18T05:00:00-04:00
+---
+
+Produces an array of objects from an object and one of its array-valued properties.
+
+- Use object destructuring to exclude the key-value pair for the specified `key` from the object.
+- Use `Array.prototype.map()` for the values of the given `key` to create an array of objects.
+- Each object contains the original object's values, except for `key` which is mapped to its individual values.
+
+```js
+const unwind = (key, obj) => {
+  const { [key]: _, ...rest } = obj;
+  return obj[key].map(val => ({ ...rest, [key]: val }));
+};
+```
+
+```js
+unwind('b', { a: true, b: [1, 2] }); // [{ a: true, b: 1 }, { a: true, b: 2 }]
+```