diff --git a/snippets/slugify.md b/snippets/slugify.md
new file mode 100644
index 000000000..4bd803463
--- /dev/null
+++ b/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'
+```
diff --git a/snippets/yesterday.md b/snippets/yesterday.md
index b343d4cb7..8fd6d3088 100644
--- a/snippets/yesterday.md
+++ b/snippets/yesterday.md
@@ -10,7 +10,7 @@ Results in a string representation of yesterday's date.
 
 ```js
 const yesterday = () => {
-  let t = new Date();
+  const t = new Date();
   t.setDate(t.getDate() - 1);
   return t.toISOString().split('T')[0];
 };