An attempt to create a flowtype definition for the fetchAPI

isomorphic-fetch.js

// flow-typed signature: 11e550b72570f3e50044485062a42c26
// flow-typed version: 33aa7c82cd/isomorphic-fetch_v2.x.x/flow_>=v0.27.x

declare type $Fetch$RequestMode = 'cors' | 'no-cors' | 'cors-with-forced-preflight' | 'same-origin' | 'navigate';
declare type $Fetch$RequestCredentials = 'omit' | 'same-origin' | 'include';
declare type $Fetch$RequestRedirect = 'follow' | 'error' | 'manual';
declare type $Fetch$RequestCache = 'default' | 'no-store' | 'reload' | 'no-cache' | 'force-cache';
declare type $Fetch$ResponseType = 'basic' | 'cors' | 'error' | 'opaque';
declare type $Fetch$ReferrerPolicy = 'no-referrer' | 'no-referrer-when-downgrade' | 'origin' |
    'origin-when-cross-origin' | 'unsafe-url';

declare class $Fetch$Headers {
    Headers(): $Fetch$Headers;
    append(name: string, value: any): void;
    delete(name: string): void;
    entries(): Iterator<*>;
    get(name: string): string;
    getAll(name: string): Array<string>;
    has(name: string): Boolean;
    keys(): Iterator<string>;
    set(name: string, value: any): void;
    values(): Iterator<*>;
}

declare class $Fetch$Body {
    bodyUsed: Boolean;
    arrayBuffer(): Promise<ArrayBuffer>;
    blob(): Promise<Blob>;
    formData(): Promise<FormData>;
    json(): Promise<JSON>;
    text(): Promise<string>;
}

declare class $Fetch$Request mixins $Fetch$Body {
    Request(): $Fetch$Request;
    clone(): $Fetch$Request;
    method: string;
    url: string;
    headers: $Fetch$Headers;
    referrer: string;
    referrerPolicy: string;
    mode: $Fetch$RequestMode;
    credentials: $Fetch$RequestCredentials;
    redirect: $Fetch$RequestRedirect;
    integrity: string;
    cache: $Fetch$RequestCache;
}

declare type $Fetch$Options = {
    method?: string,
    headers?: $Fetch$Headers,
    body?: Blob | ArrayBuffer | FormData | URLSearchParams | string,
    mode?: $Fetch$RequestMode | Object,
    credentials?: $Fetch$RequestCredentials,
    cache?: $Fetch$RequestCache,
    redirect?: $Fetch$RequestRedirect,
    referrer?: string,
    referrerPolicy?: $Fetch$ReferrerPolicy,
    integrity?: string,
}

declare class $Fetch$Response mixins $Fetch$Body {
    Response(): $Fetch$Response;
    clone(): $Fetch$Response;
    error(): $Fetch$Response;
    redirect(url: string, status?: number): $Fetch$Response;
    headers: $Fetch$Headers;
    ok: Boolean;
    redirected: Boolean;
    status: number;
    statusText: string;
    type: $Fetch$ResponseType;
    url: string;
}

declare var fetch: (url: string, options?: $Fetch$Options) => Promise<$Fetch$Response>;

declare module 'isomorphic-fetch' {
    declare module.exports: fetch;
}