How to declare an array type that can contain either a string or other array?

Issue

Here is the variable declaration with type any:

let errorMessagesBag: any = []

erroMessagesBag must be able to hold a variable number of values that can be either a string, or a tuple of strings. Example

let errorMessagesBag = ["string1", ["tuplestring1", "otherString"], "string2"] // and so on

How to replace 'any' with proper type declaration in this case, so it accepts an array that contains strings OR a tuples of strings ?

Solution

With union types:

let errorMessagesBag: (string | string[])[] = []

or

let errorMessagesBag: Array<string | string[]> = []

The two syntaxes are equivalent.

Answered By - Paleo