Make sure that prop is a value from a constant - TS

Question

I have a const in a library (blueprintjs).

export const Intent = {
    NONE: "none" as "none",
    PRIMARY: "primary" as "primary",
    SUCCESS: "success" as "success",
    WARNING: "warning" as "warning",
    DANGER: "danger" as "danger",
};
export type Intent = typeof Intent[keyof typeof Intent];

I want to make sure that my prop which I receive from my parent only has one of the 5 key values of Intent. How do I proceed forward with this? Please advice.

This is what I have done so far.

interface Props {
  exportButtonColor?: [keyof typeof Intent];
}

Any help is greatly appreciated.

[Typescript has enums...](https://www.typescriptlang.org/docs/handbook/enums.html) and declaring a type with literals means that the only valid value is that literal. — Jared Smith, Mar 20 '20 at 15:56
But your example is exporting a type...? Is that exported by the library, or did you add that yourself, and if so where? — Jared Smith, Mar 20 '20 at 15:59
https://github.com/palantir/blueprint/blob/develop/packages/core/src/common/intent.ts — arunmmanoharan, Mar 20 '20 at 16:00
Not sure what your question is? `keyof typeof Intent` is `"NONE" | "PRIMARY" | "SUCCESS" | "WARNING" | "DANGER" | undefined`, which seems to be what you want? — Jared Smith, Mar 20 '20 at 16:03
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/210012/discussion-between-a2441918-and-jared-smith). — arunmmanoharan, Mar 20 '20 at 16:04

score 1 · Accepted Answer · answered Mar 20 '20 at 17:09

Unless some very clever person has a better solution, this should work:

const Intent = {
    NONE: "none" as "none",
    PRIMARY: "primary" as "primary",
    SUCCESS: "success" as "success",
    WARNING: "warning" as "warning",
    DANGER: "danger" as "danger",
};
type Intent = typeof Intent[keyof typeof Intent];

const Classes = {
    INTENT_PRIMARY: "foobar",
    INTENT_NONE: "barfoo",
    INTENT_SUCCESS: "somecssclass",
    INTENT_WARNING: "you get the idea",
    INTENT_DANGER: "will robinson",
};

type IntentKey = keyof typeof Intent;

const KeyMap: {
    [key in IntentKey]: keyof typeof Classes
} = {
    PRIMARY: "INTENT_PRIMARY",
    NONE: "INTENT_NONE",
    SUCCESS: "INTENT_SUCCESS",
    WARNING: "INTENT_WARNING",
    DANGER: "INTENT_DANGER",
}

function test({ color }: { color: IntentKey }) {
    return Classes[KeyMap[color]];
}

Notice that this is type-safety at the cost of an explicit mapping.

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Make sure that prop is a value from a constant - TS

1 Answers1