Angular: how to define two possible values for a string variable

Question

Is it possible to define a variable with the type string and then define which possible values that string can have?

colorScheme?: string = 'positive|negative'; //must be a string 
                                             and must have the value "positive" or "negative"

Thank you.

UPDATE It does not appear to work when defined in a component:

type ColorScheme = 'positive' | 'negative';

export class MyButtonComponent {
      @Input() colorScheme?: ColorScheme;

Now it is correct. Thank you.

that's where you put whatever value you want to assign initially — Tobias S.
– Tobias S., Commented Jul 6, 2022 at 17:16
Can you write what to write? colorScheme?: 'positive' | 'negative = positive' ? Thank you. — user12950273
– user12950273, Commented Jul 6, 2022 at 17:45
yes, exactly: colorScheme?: 'positive' | 'negative' = "positive" — Tobias S.
– Tobias S., Commented Jul 6, 2022 at 17:46

Matthieu Riegler · Accepted Answer · 2022-07-05 15:32:28Z

1

Yes, it's called a union type !

type ColorScheme = 'positive' | 'negative';

const scheme1: ColorScheme = 'negative'; // ok
const scheme2: ColorScheme = 'positive'; // ok 
const scheme3: ColorScheme = 'foobar'; // ko

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answered Jul 5, 2022 at 15:32

Matthieu Riegler

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1 Comment

user12950273 Over a year ago

Sorry, i misunderstood here to place the type. Thank you.

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