The get()
method of the Headers
interface returns a byte string of all the values of a header within a Headers
object with a given name. If the requested header doesn't exist in the Headers
object, it returns null
.
For security reasons, some headers can only be controlled by the user agent. These headers include the forbidden header names and forbidden response header names.
A String
sequence representing the values of the retrieved header or null
if this header is not set.
Creating an empty Headers
object is simple:
const myHeaders = new Headers();
myHeaders.get("Not-Set");
You could add a header to this using Headers.append
, then retrieve it using get()
:
myHeaders.append("Content-Type", "image/jpeg");
myHeaders.get("Content-Type");
If the header has multiple values associated with it, the byte string will contain all the values, in the order they were added to the Headers object:
myHeaders.append("Accept-Encoding", "deflate");
myHeaders.append("Accept-Encoding", "gzip");
myHeaders.get("Accept-Encoding");
myHeaders
.get("Accept-Encoding")
.split(",")
.map((v) => v.trimStart());