update filename in a url with jquery

Wonder how I could do the following wit jquery -

I have a url pointing to an image -> http://www.website.c开发者_C百科om/folder/folder2/image_current.jpg (this value is stored in a variable)

I have variable that holds the value -> new_image.jpg

How can I with jquery update the full url (held in the variable) from

http://www.website.com/folder/folder2/image_current.jpg

to

http://www.website.com/folder/folder2/new_image.jpg

??

Try something like this:

var url = 'http://www.website.com/folder/folder2/image_current.jpg';
var new_image = 'new_image.jpg';

var new_url = url.replace(url.substring(url.lastIndexOf('/')+1), new_image);

this code is adding the file name at the start of url

var url = window.location.href;
    var filename = "index1.php";
    var newurl = url.replace(url.substring(url.lastIndexOf('/')+1), filename);
    $(window).resize(function resize(){
        if ($(window).width() < 800) {
            window.location.replace(newurl);
        }
    }).trigger('resize');

so the url becomes

index1.phphttp://localhost/indictrans/