feat: add getISO8601StringWithTz snippet

Signed-off-by: Ranadeep Polavarapu <ranadeep@icloud.com>

snippets/getISO8601StringTzAware.md

@@ -0,0 +1,46 @@
+---
+title: getISO8601StringTzAware
+tags: browser,node,date
+---
+
+Fetches an ISO8601 compliant datetime string with timezone awareness.
+
+_NOTE_: Use `Date.prototype.toISOString()` for UTC/GMT non-tz aware ISO8601 datetime string
+
+```js
+/**
+ * Fetch ISO8601 compliant date string with tz offset.
+ * Use `Date.prototype.toISOString()` for UTC/GMT non-tz
+ * datetime string.
+ */
+const getISO8601StringWithTz = (d) => {
+  const tzo = -d.getTimezoneOffset();
+  const dif = tzo >= 0 ? '+' : '-';
+  const pad = (num) => {
+    const norm = Math.floor(Math.abs(num));
+    // tslint:disable-next-line:no-magic-numbers
+    return (norm < 10 ? '0' : '') + norm;
+  };
+  return (
+    d.getFullYear() +
+    '-' +
+    pad(d.getMonth() + 1) +
+    '-' +
+    pad(d.getDate()) +
+    'T' +
+    pad(d.getHours()) +
+    ':' +
+    pad(d.getMinutes()) +
+    ':' +
+    pad(d.getSeconds()) +
+    dif +
+    pad(tzo / 60) +
+    ':' +
+    pad(tzo % 60)
+  );
+};
+```
+
+```js
+getISO8601StringWithTz(new Date()); // "2020-10-06T20:43:33-04:00"
+```