typescript - How to check if a given string key exists in Enum?

Question

I have an enum defined like this:

export enum someEnum {
    None = <any>'',
    value1 = <any>'value1',
    value2 = <any>'value2',
    value3 = <any>'value3'   
}

For example, I want to check "value4" key exists in an enum. I should get false as value4 is not defined on the enum.

I tried if (someEnum['value4']) but got an error:

Element implicitly has an 'any' type because index expression is not of type 'number'.

Answer 1

You could use the in operator:

if ('value4' in someEnum) {
  // ...
}