how to use jmeter with ajax request

How to use JMeter with ajax request?

I have a button with is clicked and by using fiddler I can find the session id which is being sent to the server.

What should I do next using the JMeter in order to handle this.

EDIT:

Let's say开发者_运维技巧 I have in my hand the header which call the request. The JSESSIONID AJAXREQUEST and so on where should I put it ?... I putted it in http header manager name and value.

Jmeter will not execute Javascript embedded in your web page. However AJAX request is also a HTTP request that Jmeter will be able to run as a separate HTTP request and upon getting the response you can have post processors (using XPATH or REGEX) to extract the session id in a Jmeter variable.

Alternatively you can record the Jmeter scripts using Jmeter proxy and then all the HTTP requests will be recorded for you and you will just need to attach a post processor manually.