feat: add slugify and use const in yesterday

snippets/slugify.md

@@ -0,0 +1,27 @@
+---
+title: slugify
+tags: function,intermediate
+---
+
+Convert a string to a URL-friendly slug.
+
+- Make the string lowercase and remove leading or trailing whitespace.
+- Remove all characters that are not words, whitespace or hyphens.
+- Replace whitespace with a single hyphen (`-`).
+- Remove any leading or trailing hyphens.
+
+```js
+const slugify = (string) => {
+  const slug = string
+    .toLowerCase()
+    .trim()
+    .replace(/[^\w\s-]/g, '')
+    .replace(/[\s_-]+/g, '-')
+    .replace(/^-+|-+$/g, '');
+  return slug;
+};
+```
+
+```js
+slugify('Hello World!'); // 'hello-world'
+```