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.
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.
- The name of the header whose value is to be set.
- The value to set as the body of the header.
The definition of 'setRequestHeader()' in that specification.
|Living Standard||WHATWG living standard|
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