Read javascript value in a page then post it back using http protocol

I have a PHP page that has many javascript variables and I want to read a specific javascript variable then post this value using HTTP post.

I know how to post the value using Indy but I don't know how to read JS variable. Please advise w开发者_如何学编程hat tool I should use, any code snippet would be much appreciated.

Unless the JS variable is assigned a static value in its code (in which case, just grep the JS code for what you need), then you will have to actually execute the JS code using a real JS scripting engine, just like a webbrowser would.