is-has


Set of checking functions. No deps! Never throws errors!

Installation

``shell
npm i is-has
`

Functions

* hasOwnProperty
* isArray
* isNumber
* isString

$3

`typescript
declare function hasOwnProperty(obj: T, key: keyof T): key is keyof T;
declare function hasOwnProperty(obj: any, key: any): key is keyof obj;
`

hasOwnProperty checks if obj has its own property. The result is fully compatible with Object.hasOwn.

`typescript
import {hasOwnProperty} from 'is-has';

class Class1 {
propA: string = 'propA';
static propB: string = 'static propB';
#propC: string = '#propC';
static #propD: string = 'static #propD';

get propC() {
return this.#propC;
}

static get propD() {
return this.#propD;
}

functionA() {
return 'functionA';
}

static functionB() {
return 'functionB';
}
}

hasOwnProperty(Class1, 'propA'); // false
hasOwnProperty(Class1, 'propB'); // true
hasOwnProperty(Class1, 'propC'); // false
hasOwnProperty(Class1, 'propD'); // true
hasOwnProperty(Class1, 'functionA'); // false
hasOwnProperty(Class1, 'functionB'); // true

const classInstance = new Class1();

hasOwnProperty(classInstance, 'propA'); // true
hasOwnProperty(classInstance, 'propB'); // false
hasOwnProperty(classInstance, 'propC'); // false
hasOwnProperty(classInstance, 'propD'); // false
hasOwnProperty(classInstance, 'functionA'); // false
hasOwnProperty(classInstance, 'functionB'); // false

const obj = {
propA: 'propA',
get propB() {
return 'propB';
},
};

hasOwnProperty(obj, 'propA'); // true
hasOwnProperty(obj, 'propB'); // true
hasOwnProperty(obj, 'propC'); // false
hasOwnProperty(obj, null); // false

const arr = [1, '2', 3, 'aaa'];

hasOwnProperty(arr, 0); // true
hasOwnProperty(arr, 4); // false
hasOwnProperty(arr, 'length'); // true
hasOwnProperty(arr, 'aaa'); // false
hasOwnProperty(arr, null); // false
hasOwnProperty(arr, undefined); // false

hasOwnProperty('obj', 'propA'); // false
hasOwnProperty(123, 'propC'); // false
hasOwnProperty(null, null); // false
hasOwnProperty(undefined, undefined); // false
`

$3

`typescript
declare function isArray(variable?: unknown): variable is Array;
`

isArray checks if variable is an array.

`typescript
import {isArray} from 'is-has';

isArray(123); // false
isArray([]); // true
isArray(['Hello!']); // true
`

$3

`typescript
declare function isNumber(variable?: unknown): variable is number;
`

isNumber checks if a variable is a number.

- Both Infinity and NaN are treated as non-numbers.
- BigInt is a separate story in JS, so it's not treated as a number as well.

`typescript
import {isNumber} from 'is-has';

isNumber(0); // true
isNumber('0'); // false
isNumber('hi'); // false
isNumber(0 / 0); // false
isNumber(1 / 0); // false
isNumber(123n); // false
`

$3

`typescript
declare function isString(variable?: unknown): variable is string;
`

isString checks if variable is a string.

`typescript
import {isString} from 'is-has';

isString(123); // false
isString('Hello!'); // true
``