To extract a body and a Content-Type value from object, with an optional boolean keepalive (default false), run these steps:
Return the result of getting name from this’s header list.If this’s guard is 'immutable', then throw a TypeError.If name is not a name, then throw a TypeError.If header does not contain exactly two items, then throw a TypeError.If object is a sequence, then for each header in object:.To fill a Headers object headers with a given object object, run these steps: If headers’s guard is 'immutable', then throw a TypeError.įilling Headers object headers with a given object object:.If name is not a name or value is not a value, then throw a TypeError.To append a name/value name/value pair to a Headers object (headers), run these steps: Otherwise, if stream is readable, error stream with a TypeError. To perform an HTTP-network fetch using request with an optional credentials flag, run these steps:ģ. Relevant passages as of January 2021 are below. The Fetch spec lists times when you throw a TypeError from the Fetch API: I understand this question might have a React-specific cause, but it shows up first in search results for 'Typeerror: Failed to fetch' and I wanted to lay out all possible causes here.
