34 lines
1005 B
Markdown
34 lines
1005 B
Markdown
---
|
|
title: Check if value is of type
|
|
tags: type,array
|
|
expertise: intermediate
|
|
cover: blog_images/coffee-phone-tray.jpg
|
|
firstSeen: 2018-01-17T21:23:46+02:00
|
|
lastUpdated: 2020-10-20T23:02:01+03:00
|
|
---
|
|
|
|
Checks if the provided value is of the specified type.
|
|
|
|
- Ensure the value is not `undefined` or `null` using `Array.prototype.includes()`.
|
|
- Use `Object.prototype.constructor` to compare the constructor property on the value with `type` to check if the provided value is of the specified `type`.
|
|
|
|
```js
|
|
const is = (type, val) => ![, null].includes(val) && val.constructor === type;
|
|
```
|
|
|
|
```js
|
|
is(Array, [1]); // true
|
|
is(ArrayBuffer, new ArrayBuffer()); // true
|
|
is(Map, new Map()); // true
|
|
is(RegExp, /./g); // true
|
|
is(Set, new Set()); // true
|
|
is(WeakMap, new WeakMap()); // true
|
|
is(WeakSet, new WeakSet()); // true
|
|
is(String, ''); // true
|
|
is(String, new String('')); // true
|
|
is(Number, 1); // true
|
|
is(Number, new Number(1)); // true
|
|
is(Boolean, true); // true
|
|
is(Boolean, new Boolean(true)); // true
|
|
```
|