185 lines
3.2 KiB
Markdown
185 lines
3.2 KiB
Markdown
# is
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Type checking utilities
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- [isBN](#isbn) Tests for a `BN` object instance.
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- [isBuffer](#isbuffer) Tests for a `Buffer` object instance.
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- [isError](#iserror) Tests for a `Error` object instance.
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- [isFunction](#isfunction) Tests for a `function`.
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- [isHex](#ishex) Tests for a hex string.
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- [isInstanceOf](#isinstanceof) Tests for a instance of a class.
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- [isNumber](#isnumber) Tests for a JavaScript number.
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- [isString](#isstring) Tests for a string.
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- [isUint8Array](#isuint8array) Tests for a `Uint8Array` object instance.
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- [isUndefined](#isundefined) Tests for a `undefined` values.
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## isBN
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Tests for a `BN` object instance.
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```js
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isBN (value: any): boolean
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```
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Checks to see if the input object is an instance of `BN` (bn.js).
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```js
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import BN from 'bn.js';
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import { isBN } from '@polkadot/util';
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console.log('isBN', isBN(new BN(1))); // => true
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```
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## isBuffer
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Tests for a `Buffer` object instance.
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```js
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isBuffer (value: any): boolean
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```
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Checks to see if the input object is an instance of `Buffer`.
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```js
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import { isBuffer } from '@polkadot/util';
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console.log('isBuffer', isBuffer(Buffer.from([]))); // => true
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```
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## isError
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Tests for a `Error` object instance.
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```js
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isError (value: any): boolean
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```
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Checks to see if the input object is an instance of `Error`.
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```js
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import { isError } from '@polkadot/util';
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console.log('isError', isError(new Error('message'))); // => true
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```
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## isFunction
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Tests for a `function`.
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```js
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isFunction (value: any): boolean
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```
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Checks to see if the input value is a JavaScript function.
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```js
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import { isFunction } from '@polkadot/util';
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console.log('isFunction', isFunction(() => false)); // => true
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```
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## isHex
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Tests for a hex string.
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```js
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isHex (value: any): boolean
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```
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Checks to see if the input value is a `0x` prefixed hex string.
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```js
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import { isHex } from '@polkadot/util';
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console.log('isHex', isHex('0x1234')); // => true
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```
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## isInstanceOf
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Tests for a instance of a class.
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```js
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isInstanceOf (value: any, clazz: any): boolean
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```
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Checks to see if the input value is an instance of the test class.
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```js
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import { isInstanceOf } from '@polkadot/util';
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console.log('isinstanceOf', isInstanceOf(new Array(0), Array)); // => true
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```
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## isNumber
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Tests for a JavaScript number.
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```js
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isNumber (value: any): boolean
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```
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Checks to see if the input value is a valid number.
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```js
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import { isNumber } from '@polkadot/util';
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console.log('isNumber', isNumber(1234)); // => true
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```
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## isString
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Tests for a string.
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```js
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isString (value: any): boolean
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```
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Checks to see if the input value is a JavaScript string.
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```js
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import { isString } from '@polkadot/util';
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console.log('isString', isString('test')); // => true
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```
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## isUint8Array
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Tests for a `Uint8Array` object instance.
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```js
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isUint8Array (value: any): boolean
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```
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Checks to see if the input object is an instance of `Uint8Array`.
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```js
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import { isUint8Array } from '@polkadot/util';
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console.log('isUint8Array', isUint8Array([])); // => false
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```
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## isUndefined
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Tests for a `undefined` values.
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```js
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isUndefined (value: any): boolean
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```
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Checks to see if the input value is `undefined`.
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```js
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import { isUndefined } from '@polkadot/util';
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console.log('isUndefined', isUndefined(void(0))); // => true
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``` |