JS Ajax: local vs absolute path issue when using SEO friendly urls

here's the thing:

i built my site with SEO friendly urls...but i have problem now calling ajax files becaus eth epath is wrong and I cant set an absolute url when i call my files in background..

for instance my page is here (similar to StackOverflow..)

www.domain.com/product/123/this-is-a-product

but my javascripts functions, in folder /js,now they try to reach the files but they cant obvisouly because are set to relative path...

how can i solve this issue??

EDIT: Found this How to g开发者_Python百科et the root path in JavaScript?

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When you are using freindly urls, then you have to use path started with /. But then you are starting path from main path.