I've write this script to redirect all url that not contain &param=param1 to url adding &param=param1 I have two questions.

1. How can I add more domain to rewrite?
2. I want that if in url are present &param=*** script remove previously parameters and sobstitute with mine (&param=xyz will be &param=param1).. it's possible?

chrome.webRequest.onBeforeRequest.addListener(
    function(details) {
        return {
            redirectUrl: details.url + 
                (details.url.indexOf("?") == -1 ? "?" : "") +
                (details.url.indexOf("&param=param1") == -1 ? "&param=param1" : "")
        };
    },
    {urls: ['*://*.mysite.it/*'], types: ['main_frame']},
    ['blocking']

);