Array of allowed values

Question

Say I have the following two types:

type OrganizationType = 'NGO' | 'Business';
type Organization = {
    name: string,
    type: OrganizationType,
    weekdaysOpen: string[],
};

How can I define weekdaysOpen such that its elements are restricted to any (or none) of some predefined values? In this case they would be:

// Allowed elements in weekdaysOpen
'mon', 'tue', 'wed', 'thu', 'fri', 'sat', 'sun'

Bonus if each allowed value can only appear once.

maybe you need an enum - typescriptlang.org/docs/handbook/enums.html — Kay
– Kay, Commented Sep 6, 2020 at 15:54

Viet Dinh · Accepted Answer · 2020-09-06 15:54:56Z

2

You can try with:

type OrganizationType = 'NGO' | 'Business';
type WeekDay = 'mon' | 'tue' | 'wed' | 'thu' | 'fri' | 'sat' | 'sun';
type Organization = {
    name: string,
    type: OrganizationType,
    weekdaysOpen: WeekDay[],
};

answered Sep 6, 2020 at 15:54

Viet Dinh

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Comments

pzaenger · Accepted Answer · 2020-09-06 15:55:50Z

1

You could use a Set to allow only unique values:

type WeekDay = 'mon' | 'tue' | 'wed' | 'thu' | 'fri' | 'sat' | 'sun';

type Organization = {
  ...
  weekdaysOpen: Set<WeekDay>
};

answered Sep 6, 2020 at 15:55

pzaenger

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1 Comment

RobertK Over a year ago

Very elegant, thank you! Regardless, I'm in awe by all these quality suggestions appearing so quickly, thanks everyone!

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