ghaction-upx/node_modules/@sindresorhus/is/readme.md
2020-01-17 09:39:25 +01:00

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# is [![Build Status](https://travis-ci.org/sindresorhus/is.svg?branch=master)](https://travis-ci.org/sindresorhus/is)
> Type check values: `is.string('🦄') //=> true`
<img src="header.gif" width="182" align="right">
## Install
```
$ npm install @sindresorhus/is
```
## Usage
```js
const is = require('@sindresorhus/is');
is('🦄');
//=> 'string'
is(new Map());
//=> 'Map'
is.number(6);
//=> true
```
## API
### is(value)
Returns the type of `value`.
Primitives are lowercase and object types are camelcase.
Example:
- `'undefined'`
- `'null'`
- `'string'`
- `'symbol'`
- `'Array'`
- `'Function'`
- `'Object'`
Note: It will throw if you try to feed it object-wrapped primitives, as that's a bad practice. For example `new String('foo')`.
### is.{method}
All the below methods accept a value and returns a boolean for whether the value is of the desired type.
#### Primitives
##### .undefined(value)
##### .null(value)
##### .string(value)
##### .number(value)
##### .boolean(value)
##### .symbol(value)
#### Built-in types
##### .array(value)
##### .function(value)
##### .buffer(value)
##### .object(value)
Keep in mind that [functions are objects too](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions).
##### .regExp(value)
##### .date(value)
##### .error(value)
##### .nativePromise(value)
##### .promise(value)
Returns `true` for any object with a `.then()` and `.catch()` method. Prefer this one over `.nativePromise()` as you usually want to allow userland promise implementations too.
##### .generator(value)
Returns `true` for any object that implements its own `.next()` and `.throw()` methods and has a function definition for `Symbol.iterator`.
##### .generatorFunction(value)
##### .asyncFunction(value)
Returns `true` for any `async` function that can be called with the `await` operator.
```js
is.asyncFunction(async () => {});
// => true
is.asyncFunction(() => {});
// => false
```
##### .boundFunction(value)
Returns `true` for any `bound` function.
```js
is.boundFunction(() => {});
// => true
is.boundFunction(function () {}.bind(null));
// => true
is.boundFunction(function () {});
// => false
```
##### .map(value)
##### .set(value)
##### .weakMap(value)
##### .weakSet(value)
#### Typed arrays
##### .int8Array(value)
##### .uint8Array(value)
##### .uint8ClampedArray(value)
##### .int16Array(value)
##### .uint16Array(value)
##### .int32Array(value)
##### .uint32Array(value)
##### .float32Array(value)
##### .float64Array(value)
#### Structured data
##### .arrayBuffer(value)
##### .sharedArrayBuffer(value)
##### .dataView(value)
#### Miscellaneous
##### .directInstanceOf(value, class)
Returns `true` if `value` is a direct instance of `class`.
```js
is.directInstanceOf(new Error(), Error);
//=> true
class UnicornError extends Error {};
is.directInstanceOf(new UnicornError(), Error);
//=> false
```
##### .truthy(value)
Returns `true` for all values that evaluate to true in a boolean context:
```js
is.truthy('🦄');
//=> true
is.truthy(undefined);
//=> false
```
##### .falsy(value)
Returns `true` if `value` is one of: `false`, `0`, `''`, `null`, `undefined`, `NaN`.
##### .nan(value)
##### .nullOrUndefined(value)
##### .primitive(value)
JavaScript primitives are as follows: `null`, `undefined`, `string`, `number`, `boolean`, `symbol`.
##### .integer(value)
##### .safeInteger(value)
Returns `true` if `value` is a [safe integer](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger).
##### .plainObject(value)
An object is plain if it's created by either `{}`, `new Object()`, or `Object.create(null)`.
##### .iterable(value)
##### .class(value)
Returns `true` for instances created by a ES2015 class.
##### .typedArray(value)
##### .arrayLike(value)
A `value` is array-like if it is not a function and has a `value.length` that is a safe integer greater than or equal to 0.
```js
is.arrayLike(document.forms);
//=> true
function () {
is.arrayLike(arguments);
//=> true
}
```
##### .inRange(value, range)
Check if `value` (number) is in the given `range`. The range is an array of two values, lower bound and upper bound, in no specific order.
```js
is.inRange(3, [0, 5]);
is.inRange(3, [5, 0]);
is.inRange(0, [-2, 2]);
```
##### .inRange(value, upperBound)
Check if `value` (number) is in the range of `0` to `upperBound`.
```js
is.inRange(3, 10);
```
##### .domElement(value)
Returns `true` if `value` is a DOM Element.
##### .nodeStream(value)
Returns `true` if `value` is a Node.js [stream](https://nodejs.org/api/stream.html).
```js
const fs = require('fs');
is.nodeStream(fs.createReadStream('unicorn.png'));
//=> true
```
##### .infinite(value)
Check if `value` is `Infinity` or `-Infinity`.
##### .even(value)
Returns `true` if `value` is an even integer.
##### .odd(value)
Returns `true` if `value` is an odd integer.
##### .empty(value)
Returns `true` if `value` is falsy or an empty string, array, object, map, or set.
##### .emptyOrWhitespace(value)
Returns `true` if `is.empty(value)` or a string that is all whitespace.
##### .any(predicate, ...values)
Returns `true` if **any** of the input `values` returns true in the `predicate`:
```js
is.any(is.string, {}, true, '🦄');
//=> true
is.any(is.boolean, 'unicorns', [], new Map());
//=> false
```
##### .all(predicate, ...values)
Returns `true` if **all** of the input `values` returns true in the `predicate`:
```js
is.all(is.object, {}, new Map(), new Set());
//=> true
is.all(is.string, '🦄', [], 'unicorns');
//=> false
```
## FAQ
### Why yet another type checking module?
There are hundreds of type checking modules on npm, unfortunately, I couldn't find any that fit my needs:
- Includes both type methods and ability to get the type
- Types of primitives returned as lowercase and object types as camelcase
- Covers all built-ins
- Unsurprising behavior
- Well-maintained
- Comprehensive test suite
For the ones I found, pick 3 of these.
The most common mistakes I noticed in these modules was using `instanceof` for type checking, forgetting that functions are objects, and omitting `symbol` as a primitive.
## Related
- [is-stream](https://github.com/sindresorhus/is-stream) - Check if something is a Node.js stream
- [is-observable](https://github.com/sindresorhus/is-observable) - Check if a value is an Observable
- [file-type](https://github.com/sindresorhus/file-type) - Detect the file type of a Buffer/Uint8Array
- [is-ip](https://github.com/sindresorhus/is-ip) - Check if a string is an IP address
- [is-array-sorted](https://github.com/sindresorhus/is-array-sorted) - Check if an Array is sorted
- [is-error-constructor](https://github.com/sindresorhus/is-error-constructor) - Check if a value is an error constructor
- [is-empty-iterable](https://github.com/sindresorhus/is-empty-iterable) - Check if an Iterable is empty
- [is-blob](https://github.com/sindresorhus/is-blob) - Check if a value is a Blob - File-like object of immutable, raw data
- [has-emoji](https://github.com/sindresorhus/has-emoji) - Check whether a string has any emoji
## Created by
- [Sindre Sorhus](https://github.com/sindresorhus)
- [Giora Guttsait](https://github.com/gioragutt)
- [Brandon Smith](https://github.com/brandon93s)
## License
MIT