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snippets/javascript-blank-value.md

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+---
+title: How can I check for a blank value in JavaScript?
+shortTitle: Value is blank
+type: question
+tags: [javascript,type]
+author: chalarangelo
+cover: workspace-with-speaker
+excerpt: JavaScript doesn't have a built-in way to check if a value is blank, but it's easy to create one.
+dateModified: 2022-09-25T05:00:00-04:00
+---
+
+JavaScript doesn't have a built-in way to check if a value is blank, but it's easy to create one. Before we do, however, we should define the behavior of such a method. The inspiration for this comes from Rails' `blank?` method, but modified to fit JavaScript's needs.
+
+First of all, any falsy values should be considered blank. These include `null`, `undefined`, `0`, `false`, `''`, and `NaN`.
+
+```js
+const isFalsy = value => !value;
+
+isFalsy(null); // true
+isFalsy(undefined); // true
+isFalsy(0); // true
+isFalsy(false); // true
+isFalsy(''); // true
+isFalsy(NaN); // true
+```
+
+Secondly, empty arrays and objects should also be considered blank. This can be easily checked by using `Object.keys()` for both types of values.
+
+```js
+const isEmptyCollection = value =>
+  (Array.isArray(value) || value === Object(value)) &&
+  !Object.keys(value).length;
+
+isEmptyCollection([]); // true
+isEmptyCollection({}); // true
+```
+
+In addition to the empty string (`''`), whitespace-only strings should be considered blank, too. A regular expression can be used to check for this.
+
+```js
+const isWhitespaceString = value =>
+  typeof value === 'string' && /^\s*$/.test(value);
+
+isWhitespaceString(' '); // true
+isWhitespaceString('\t\n\r'); // true
+```
+
+Finally, we can check for some commonly-used built-in objects. Invalid `Date` instances, as well as empty `Set` and `Map` instances should all be considered blank.
+
+```js
+const isInvalidDate = value =>
+  value instanceof Date && Number.isNaN(value.getTime());
+const isEmptySet = value => value instanceof Set && value.size === 0;
+const isEmptyMap = value => value instanceof Map && value.size === 0;
+
+isInvalidDate(new Date('hello')); // true
+isEmptySet(new Set()); // true
+isEmptyMap(new Map()); // true
+```
+
+Putting everything together, we can finally set up our `isBlank` method.
+
+```js
+const isFalsy = value => !value;
+const isWhitespaceString = value =>
+  typeof value === 'string' && /^\s*$/.test(value);
+const isEmptyCollection = value =>
+  (Array.isArray(value) || value === Object(value)) &&
+  !Object.keys(value).length;
+const isInvalidDate = value =>
+  value instanceof Date && Number.isNaN(value.getTime());
+const isEmptySet = value => value instanceof Set && value.size === 0;
+const isEmptyMap = value => value instanceof Map && value.size === 0;
+
+const isBlank = value => {
+  if (isFalsy(value)) return true;
+  if (isWhitespaceString(value)) return true;
+  if (isEmptyCollection(value)) return true;
+  if (isInvalidDate(value)) return true;
+  if (isEmptySet(value)) return true;
+  if (isEmptyMap(value)) return true;
+  return false;
+};
+
+isBlank(null); // true
+isBlank(undefined); // true
+isBlank(0); // true
+isBlank(false); // true
+isBlank(''); // true
+isBlank(' \r\n '); // true
+isBlank(NaN); // true
+isBlank([]); // true
+isBlank({}); // true
+isBlank(new Date('hello')); // true
+isBlank(new Set()); // true
+isBlank(new Map()); // true
+```