JavaScript: The Definitive Guide, 5th Edition

Name

XMLHttpRequest.send( ): send an HTTP request

Synopsis

void send(Objectbody)

Arguments

body

If the HTTP method specified by the call to open( ) is “POST” or “PUT”, this argument specifies the body of the request, as a string or Document object, or null if no body is necessary. For any other method, this argument is unused and should be null. (Some implementations do not allow you to omit this argument.)

Description

This method causes an HTTP request to be issued. If there has been no previous call to open( ), or, more generally, if readyState is not 1, send( ) throws an exception. Otherwise, it issues an HTTP request that consists of:

• The HTTP method, URL, and authorization credentials (if any) specified in the previous call to open( )

• The request headers, if any, specified by previous calls to setRequestHeader( )

• The body argument passed to this method

Once the request has been issued, send( ) sets readyState to 2 and triggers the onreadystatechange event handler.

If the async argument to the previous call to open( ) was false, this method blocks and does not return until readyState is 4 and the server’s response has been fully received. Otherwise, if the async argument is true or if that argument is omitted, send( ) returns immediately, and the server’s response is processed, as described next, on a background thread.

If the server responds with an HTTP redirect, the send( ) method or the background thread follow the redirect automatically. When all HTTP response headers have been received, ...