Get URL parameters value

 function getQueryVariable(variable) {
        var query = window.location.search.substring(1);
        var vars = query.split("&");
        for (var i = 0; i < vars.length; i++) {
            var pair = vars[i].split("=");
            if (pair[0] == variable) { return pair[1]; }
        }
        return (false);
    }

Usage

Example URL:
http://www.example.com/index.php?id=1&image=awesome.jpg

Calling  getQueryVariable("id") - would return "1".
Calling  getQueryVariable("image") - would return "awesome.jpg".

reference

https://css-tricks.com/snippets/javascript/get-url-variables/