Typed Fetch

Typed Fetch addresses the issue of flow not being able to validate the types of the data that an API call responds with. The package exposes the typedFetch function which mimics the fetch API but additionally accepts a decoder. If the response data's type is the expected type, the response is a promise of the decoded object. If the response json is of a different structure, an exception is raised that should be caught and handled.

Examples

import typedFetch from "typed-fetch";
import { object, string } from "decoders";

// Our response should include a title
const todosDecoder = object({ title: string });

typedFetch("https://jsonplaceholder.typicode.com/todos/1", todosDecoder)
.then(todos => {
  // todos has the flow type {| title: string |} as specified by the decoder

  const myTodos: { title: string } = todos; // passes a flow check
  const myFoo: { foo: string } = todos; // fails a flow check
})

For more examples on how decoders work, go to the decoders github page