Adding addDaysToDate snippet

snippets/addDaysToDate.md

@@ -0,0 +1,28 @@
+---
+title: addDaysToDate
+tags: date,beginner
+---
+
+Return the date of `n` days from any given date.
+
+- Use `new Date()` to read the first parameter as a valid Date
+- Add `n` number of days to the given date
+- Return the output in `yyyy-MM-dd` format by using `Date.prototype.toISOString()` and removing timestamp
+- For example, adding `15` to `1 October 2020` results to `16 October 2020`
+- Also accepts negative numbers. For example, adding `-15` to `16 October 2020` results to `1 October 2020`
+
+```js
+const addDaysToDate = (d,n) => {
+  d = new Date(d);
+  d.setDate(d.getDate() + n);
+  return d.toISOString().split('T')[0];
+}
+```
+
+```js
+addDaysToDate("2020-10-15", -10); // '2020-10-05'
+addDaysToDate("2020-10-15", 10); // '2020-10-25'
+addDaysToDate("10/15/2020", 10); // '2020-10-25'
+addDaysToDate("2020-10-31", 1); // '2020-11-01'
+addDaysToDate("12/31/2020", 31); // '2021-01-31'
+```