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snippets/js/s/initialize-mapped-array.md

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+---
+title: Initialize mapped array
+type: snippet
+language: javascript
+tags: [array]
+author: chalarangelo
+cover: yellow-shoes
+dateModified: 2023-06-13T05:00:00-04:00
+---
+
+Initializes and fills an array with the specified values, using a mapping function.
+
+- Use the `Array()` constructor to create an array of the desired length.
+- Use `Array.prototype.fill()` to fill it with `null` values.
+- Use `Array.prototype.map()` to fill it with the desired values, using the provided function, `mapFn`.
+- Omit the second argument, `mapFn`, to map each element to its index.
+
+```js
+const initializeMappedArray = (n, mapFn = (_, i) => i) =>
+  Array(n).fill(null).map(mapFn);
+```
+
+```js
+initializeMappedArray(5); // [0, 1, 2, 3, 4]
+initializeMappedArray(5, i => `item ${i + 1}`);
+// ['item 1', 'item 2', 'item 3', 'item 4', 'item 5']
+```