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+---
+title: isISOString
+tags: date,intermediate
+---
+
+Checks if the given string is valid in the simplified extended ISO format (ISO 8601).
+
+- Use `new Date()` to create a date object from the given string.
+- Use `Date.prototype.valueOf()` and `Number.isNaN()` to check if the produced date object is valid.
+- Use `Date.prototype.toISOString()` to compare the ISO formatted string representation of the date with the original string.
+
+```js
+const isISOString = val => {
+  const d = new Date(val);
+  return !Number.isNaN(d.valueOf()) && d.toISOString() === val;
+};
+
+```
+
+```js
+isISOString('2020-10-12T10:10:10.000Z'); // true
+isISOString('2020-10-12'); // false
+```