add isLeapYear snippet

snippets/isLeapYear.md

@@ -0,0 +1,19 @@
+---
+title: isLeapYear
+tags: function,date,beginner
+---
+
+Returns `true` if year is leap year.
+
+Use `new Date()`, set the date to 29st february `year`, check if the month is equal with 1 then return `true`
+
+```js
+const isLeapYear = (year) => {
+    return new Date(year, 1, 29).getMonth() === 1
+}
+```
+
+```js
+isLeapYear(2019); // false
+isLeapYear(2020); // true
+```