add utility for checking if a value is null or undefined

src/utilities/isNotNullish.ts

@@ -0,0 +1,15 @@
+/**
+ * This function is used to check nullish state of a value passed to it. Nullish means the value being either `null` or `undefined`. If the value is found to be nullish, the function returns the boolean `false`, else it returns the boolean `true`.
+ * @example
+ * Here's an example:-
+ * function print(str: string | null) \{
+ *   if(isNotNullish(str)) \{
+ *     console.log(`the string is ${str}`)
+ *   \} else \{
+ *     console.log(`the string is null`)
+ *   \}
+ * \}
+ */
+export function isNotNullish<T0>(value: T0 | undefined | null): value is T0 {
+	return value !== undefined && value !== null;
+}