The type of the headers variable that we're spreading here is HeadersInit | undefined.
HeadersInit is defined as:
type HeadersInit = string[][] | Record<string, string> | Headers;
What happens when we merge an array (string[][]) into an object? The array indexes become header keys. That's not the correct behaviour—we should instead use the key inside the entries array.
const a = [['a', '1']]
const b = { ...a }
JSON.stringify(b)
// => '{"0":["a","1"]}'
Desired result: { a: 1 }
What happens when we merge a Headers class into an object? We lose all data!
const a = new Headers([['a', '1']])
const b = { ...a }
JSON.stringify(b)
// => '{}'
Related: https://github.com/unsplash/unsplash-web/pull/7397
https://github.com/unsplash/unsplash-js/blob/07050e9d8d7d3655e7ca1981a8db8a827a3c6745/src/helpers/request.ts#L37-L40
The type of the
headersvariable that we're spreading here isHeadersInit | undefined.HeadersInitis defined as:What happens when we merge an array (
string[][]) into an object? The array indexes become header keys. That's not the correct behaviour—we should instead use the key inside the entries array.Desired result:
{ a: 1 }What happens when we merge a
Headersclass into an object? We lose all data!Desired result:
{ a: 1 }Related: a lint rule could have caught this https://github.com/typescript-eslint/typescript-eslint/issues/748