How to differentiate Map and string value in typescript?

Question

I am using a variable which has 2 types either string or Map. I want to check whether the variable is in type of string or Map. For that I have used the following code.

// description is like this description: string | Map<string, string>
if (description instanceof String) {
    return description;
}else {
  return description?.get('test');
}

But it gives me the following error.

Property 'get' does not exist on type 'string | Map'. Property 'get' does not exist on type 'string'

Please help me to solve the problem. Thanks.

have you tried writing: (description as Map<string, string>).get('test') — bakkaa
– bakkaa, Commented Jun 16, 2020 at 5:41

Evert · Accepted Answer · 2020-06-16 05:41:11Z

2

instanceOf String will not do the right thing, but typeof description === 'string' will, or alternatively reverse it and use instanceof Map. Not every string is a String object. Most aren't.

answered Jun 16, 2020 at 5:41

Evert

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