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+# 79. convert snake_case to camelCase
+
+### Problem
+
+https://bigfrontend.dev/problem/convert-snake_case-to-camelCase
+
+#
+
+### Problem Description
+
+Do you prefer [snake_case](https://en.wikipedia.org/wiki/Snake_case) or [camelCase](https://en.wikipedia.org/wiki/Camel_case) ?
+
+Anyway, please create a function to convert snake_case to camcelCase.
+
+```js
+snakeToCamel('snake_case');
+// 'snakeCase'
+snakeToCamel('is_flag_on');
+// 'isFlagOn'
+snakeToCamel('is_IOS_or_Android');
+// 'isIOSOrAndroid'
+snakeToCamel('_first_underscore');
+// '_firstUnderscore'
+snakeToCamel('last_underscore_');
+// 'lastUnderscore_'
+snakeToCamel('_double__underscore_');
+// '_double__underscore_'
+```
+
+contiguous underscore `__`, leading underscore `_a`, and trailing underscore `a_` should be kept untouched.
+
+#
+
+### Solution
+
+```js
+/**
+ * @param {string} str
+ * @return {string}
+ */
+function snakeToCamel(str) {
+  return str.replace(/[a-z]_[a-z]/gi, (match) => {
+    return match[0] + match[2].toUpperCase();
+  });
+}
+```
+
+#
+
+### Refactored Solution
+
+```js
+/**
+ * @param {string} str
+ * @return {string}
+ */
+function snakeToCamel(str) {
+  return str.replace(/([^_])_([^_])/g, (_, before, after) => {
+    return before + after.toUpperCase();
+  });
+}
+```
+
+#
+
+### Solution with Lookbehind
+
+```js
+/**
+ * @param {string} str
+ * @return {string}
+ */
+function snakeToCamel(str) {
+  return str.replace(/(?<=[a-z])_[a-z]/gi, (match) => {
+    return match[1].toUpperCase();
+  });
+}
+```
+
+#
+
+### Reference
+
+[Problem Discuss](https://bigfrontend.dev/problem/convert-snake_case-to-camelCase/discuss)