int_19h on Adding type safety to object IDs in TypeScript

Comment on Adding type safety to object IDs in TypeScript parent

You shouldn't need to write this kind of thing manually for every such type.

    function is<T extends string>(value: string, prefix: T): value is `${typeof prefix}_${string}` {
      return value.startsWith(`${prefix}_`)
    }

You can now do `is(id, 'user')`.

If you do that often you probably want to create separate functions, e.g.:

    function isFactory<T extends string>(prefix: T) {
      return (value: string) => is(value, prefix)
    }

    const isUser = isFactory('user')
    const isOrder = isFactory('order')

Not too bad.

Comments