StackOverflowHelp Promises

test.ts

const axios = require("axios");

class Test {
    view1: { id: number, name: string } | undefined;
    view2: { id: number, name: string } | undefined;
    view3: { id: number, name: string } | undefined;
    extra_photos: { id: number, name: string }[] | undefined

    async downloadFile(id: number, name: string): Promise<File> {
        const response = await axios({
            url: `/file/${id}`,
            method: "GET",
            responseType: "blob",
        })
        return new File([response.data], name);
    }
    async downloadFiles() {
        let extraPhotos;
        let fileView1;
        let fileView2;
        let fileView3;
        if(this.extra_photos != null){
            const files = this.extra_photos.map(async (photo) => {
                //Promise<void>
            })
            const collection = [
                this.view1 ? this.downloadFile(this.view1.id, this.view1?.name) : Promise.resolve(null),
                this.view2 ? this.downloadFile(this.view2.id, this.view2?.name) : Promise.resolve(null),
                this.view3 ? this.downloadFile(this.view3.id, this.view3?.name) : Promise.resolve(null)
            ]
            collection.concat(this.extra_photos.map((photo)=>this.downloadFile(photo.id, photo.name)));
            const res = await Promise.all(collection);
            let [fileView1, fileView2, fileView3] = res; //File | undefined
            let filesExtraPhotos = await Promise.all(
                this.extra_photos.map(
                    (photo)=>this.downloadFile(photo.id, photo.name)
                )
            ); //File[]
        }
        return {
            fileView1, 
            fileView2, 
            fileView3,
            extraPhotos
        }
    }
}