non-standard TypeScript interface/class fields

Question

I'm working on JSON-Schema-faker project where we use following TypeScript interface:

interface IGeneratorSchema { faker?: any; chance?: any; } for objects such as: { "faker": "name.findName" } or: { "chance": { "bool": { "likelihood": 100 } } }

Now we need to introduce support for x-faker and x-chance fields that would semantically mean the same as faker and chance, e.g:

{ "x-faker": "name.findName" } or: { "x-chance": { "bool": { "likelihood": 100 } } }

I know I can create neither x-faker nor x-chance field in TypeScript interface. The question is - how can I overcome that? I want TypeScript to strictly allow only those four fields: faker, chance, x-faker, x-chance.

Supported?? - github.com/Microsoft/TypeScript/issues/4653

Amit
– Amit

2016-04-13 21:30:34 +00:00
Commented Apr 13, 2016 at 21:30 — Amit
– Amit, Commented Apr 13, 2016 at 21:30

basarat · Accepted Answer · 2016-04-14 00:46:33Z

1

I want TypeScript to strictly allow only those four fields: faker, chance, x-faker, x-chance

You can declare string properties:

interface IGeneratorSchema {
    faker?: any;
    chance?: any;
    "x-faker"?: any;
    "x-chance"?: any;
}

const foo:IGeneratorSchema = { "x-faker": {} } // Okay
const bar:IGeneratorSchema = { bad: {} } // Error: unknown property

Caveat

Extra member are only prevented in fresh object literal scenarios : https://basarat.gitbooks.io/typescript/content/docs/types/freshness.html

answered Apr 14, 2016 at 0:46

basarat

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