Creating a type from nested interface properties in TypeScript

While at work I was upgrading graphql-code-generator, and found that the generated code no longer exports the type for a query node. Instead, the type of the whole query response was exported. But I had code that relied on having the node type available.

To solve this, I created a new type by reading attributes from deep in the response type.

interface Foo {
    bar: {
        baz: {
            zap: {
                zoop: number;
            }[];
        };
    };
}

type zoop = Foo['bar']['baz']['zap'][number]['zoop'];

If some of your properties are optional, you can use Required<T>. If they're possibly undefined, use Exclude<T, undefined>.

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