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snippets/js/s/map-string.md

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+---
+title: Map string
+type: snippet
+language: javascript
+tags: [string]
+cover: budapest-palace
+dateModified: 2020-10-21T21:54:53+03:00
+---
+
+Creates a new string with the results of calling a provided function on every character in the given string.
+
+- Use `String.prototype.split()` and `Array.prototype.map()` to call the provided function, `fn`, for each character in `str`.
+- Use `Array.prototype.join()` to recombine the array of characters into a string.
+- The callback function, `fn`, takes three arguments (the current character, the index of the current character and the string `mapString` was called upon).
+
+```js
+const mapString = (str, fn) =>
+  str
+    .split('')
+    .map((c, i) => fn(c, i, str))
+    .join('');
+```
+
+```js
+mapString('lorem ipsum', c => c.toUpperCase()); // 'LOREM IPSUM'
+```