Function declaration with multiple type

Question

I have the following function that takes a String and return a String such as

mockingcase('foobar')
// => fOoBaR

The project has a Typescript declaration file. I don't know much about Typescript (read nothing other than the last hour spent reading the doc.)

The function mockingcase has now the ability to return a String from an Array of string

mockingcase(['foo','bar'])
// => 'fOoBaR'

How do I change the typescript declaration file so it can take a String or an Array?

original:

function mockingcase(input: string, options?: { random?: boolean }): string;

my idea:

function mockingcase(input: string|array, options?: { random?: boolean }): string;

Am I completely wrong?

function mockingcase(input: string|string[], options?: { random?: boolean }): string — ttulka
– ttulka, Commented Feb 27, 2019 at 9:45

Joe Clay · Accepted Answer · 2019-02-27 09:44:59Z

2

You're close - array types must also define what the type of the object contained within the array is:

input: string | string[]

Or:

input: string | Array<string>

answered Feb 27, 2019 at 9:44

Joe Clay

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