https://github.github.io/fetch/#Headers
const response = await fetch("https://example.com/api")
for (const [key, value] of response.headers) {
console.log(key, value)
}
An alternative would be forEach()
response.headers.forEach((value, key) => {
console.log(value, key)
})
Or using the entries() iterator (ES8)
const headerIterator = response.headers.entries()
console.log(headerIterator.next().value)
console.log(headerIterator.next().value)
To add a new header just use set()
response.set(key, value)