feat: new function - isDef & isUndef

Author: GreatAuk

README.md

@@ -144,6 +144,8 @@ pnpm add @utopia-utils/share
 * isPlainObject
 * isObject
 * isIntegerKey
+* isUndef
+* isDef
 * isEmpty  [source](https://github.com/GreatAuk/utopia-utils/blob/main/packages/share/src/isEmpty.ts)
 * isNumberLike  [source](https://github.com/GreatAuk/utopia-utils/blob/main/packages/share/src/isNumberLike.ts)
 * isValidUrl  [source](https://github.com/GreatAuk/utopia-utils/blob/main/packages/share/src/isValidUrl.ts)

packages/share/src/is.ts

@@ -48,3 +48,7 @@ export const isStringNumber = (val: string): boolean => {
     return false
   return !Number.isNaN(Number(val))
 }
+
+export const isDef = <T>(val: T): val is NonNullable<T> => val !== undefined && val !== null
+
+export const isUndef = (val: any): val is (undefined | null) => val === undefined || val === null