XMLHttpRequest setRequestHeader() --> 有没有办法设置标头值，而不是附加到它？

Question

来自： http: //www.w3.org/TR/XMLHttpRequest/#the-setrequestheader-method

client.setRequestHeader() 
    Appends an header to the list of author request headers, or if
    header is already in the list of author request headers, combines 
    its value with value.

问：有没有一种方法可以只设置标头而不是附加到现有标头？

我正在使用的代码如下，基本上是从https://docs.djangoproject.com/en/dev/ref/contrib/csrf/#ajax复制和粘贴的：

jQuery(document).ajaxSend(function(event, xhr, settings) {
     ...

     // xhr is an XMLHttpRequest object
     xhr.setRequestHeader("X-CSRFToken", getCookie('csrftoken'));
}