add isAlphaNumeric snippet

snippets/isAlphaNumeric.md

@@ -0,0 +1,19 @@
+---
+title: isAlphaNumeric
+tags: string,regexp,intermediate
+---
+
+Checks if a string contains only alphanumeric characters.
+
+Use `String.prototype.match()` to check if input string matches against alphanumeric regex pattern.
+
+```js
+const isAlphaNumeric = (str) => !!str.match(/^[a-z0-9]+$/gi);
+```
+
+```js
+isAlphaNumeric('hello123'); // true
+isAlphaNumeric('123'); // true
+isAlphaNumeric('hello 123'); // false (space character is not alphanumeric)
+isAlphaNumeric('#$hello'); // false
+```