hi! 1. Im hiding my main contents using javascript on page load whether SE read the contents or not? 2. Due to hiding my main contents using javascript on page load whether my page rank will affect or not?
Put the website through a spider simulator tool and you would exactly know if the spiders are able to read it or not. If they get to know that you are trying to hide content (looks spammy) it might give them an indication that the page should be classified as spam. If that happens, your're rankings are gonna take a beating.
If you're hiding your content from the search engines via JavaScript (and no they can't parse them for the most part, except with the most basic of scripts which they can read) then you're doing a disservice not only to the search engines but also those users who do not have a JavaScript capable browser (such as those who have scripting stripped out via a firewall at work, mobile users, and those who use screen readers and text-based browsers like Lynx). In other words, it's not just an SEO issue but also an accessibility one as well.
Only if the content is in the HTML. If it's being generated by JavaScript dynamically, chances are near certain (as in 95%) that the search engines won't even see it. Oh, and I do need to answer the second question from the OP. No, it won't change your PageRank. Only links can do that.