XMLHttpRequest.setRequestHeader()
The XMLHttpRequest
method
setRequestHeader()
sets the value of an HTTP request
header. When using setRequestHeader()
, you must call it after calling
open()
, but before calling
send()
. If this method is called several times
with the same header, the values are merged into one single request header.
Each time you call setRequestHeader()
after the first time you call it,
the specified text is appended to the end of the existing header's content.
If no Accept
header has been set using this, an Accept
header with the type "*/*"
is sent with the request when
send()
is called.
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.
Note: For your custom fields, you may encounter a "not
allowed by Access-Control-Allow-Headers in preflight response" exception
when you send requests across domains. In this situation, you need to set up the
Access-Control-Allow-Headers
in your response header at server side.
Syntax
XMLHttpRequest.setRequestHeader(header, value)
Parameters
header
-
The name of the header whose value is to be set.
value
-
The value to set as the body of the header.
Return value
undefined
.
Specifications
Specification |
---|
XMLHttpRequest Standard # the-setrequestheader()-method |
Browser compatibility
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