Convert object to array with map with typings in TS

Question

I'm trying to convert an object of values coming from Firebase to a typed array of values:

const snapshot = await db.teams().once('value');
const teams: Array<ITeam> = Object.entries(snapshot.val()).map(
    ([id, { identifier, name }]): ITeam => {
        return { identifier, name, id };
    }
);

Types are modelled like following:

export interface ITeam extends ITeamEntry {
    id: string;
}

export interface ITeamEntry {
    identifier: string;
    name: string;
}

But I'm getting errors like:

Property 'identifier' does not exist on type 'unknown'.
Property 'name' does not exist on type 'unknown'.

I'm not sure how to fix this.

Shouldn't ILeague be a type attribute of ITeam ?

zken
– zken

2019-07-18 12:12:51 +00:00
Commented Jul 18, 2019 at 12:12 — zken
– zken, Commented Jul 18, 2019 at 12:12

Titian Cernicova-Dragomir · Accepted Answer · 2019-07-18 12:15:09Z

3

val is probably an object with unknown properties. To be able to access the properties you will probably need to assert val to Record<string, ITeam>

const teams: Array<ITeam> = Object.entries(snapshot.val() as Record<string, ITeam>).map(
    ([id, { identifier, name }]): ITeam => {
        return { identifier, name, id };
    }
);

answered Jul 18, 2019 at 12:15

Titian Cernicova-Dragomir

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1 Comment

sunpietro Over a year ago

Thanks! I was missing the Record type. I was not aware of it.

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