Question

I’m trying to do a URL GET variable replace, however the regular expression for checking whether the variable exists in amongst other GET variables is returning true when I am expecting it to return false.

The pattern I am using is: &sort=.*&

Test URL: http://localhost/search?location=any&sort=asc

Am I right to believe that this pattern should be returning false on the basis that their is no ampersand character following the sort parameter’s value?

Full code:

var sort = getOptionValue($(this).attr('id'));
var url = document.URL;

if(url.indexOf('?') == -1) {
    url = url+'?sort='+sort;
} else {
    if(url.search('/&sort=.*&/i')) {
        url.replace('/&sort=.*&/i','&sort='+sort+'&');
    }
    else if(url.search('/&sort=.*/i')) {
        url.replace('/&sort=.*/i','&sort='+sort);
    }
}

Answer 1

Am I right to believe that this pattern should be returning false on the basis that their is no ampersand character following the sort parameter’s value?

Well, you are using String.search, which, according to the linked documentation:

If successful, search returns the index of the regular expression inside the string. Otherwise, it returns -1.

So it will return -1, or 0 or greater when there is a match. So you should test for -1, not truthiness.

Also, there is no need to pass the regexes as strings, you might as well use:

url.replace(/&sort=.*&/i,'&sort='+sort+'&');

Further, keep in mind that replace will create a new string, not replace in the string (strings in Javascript are immutable).

Finally, I don’t see the need for searching for the string, and then replacing it — it seems that you always want to replace &sort=SOMETHING with &sort=SOMETHING_ELSE, so just do that:

if(url.indexOf('?') == -1) {
    url = url+'?sort='+sort;
} else {
    url = url.replace(/&sort=[^&]*/i, '&sort=' + sort);
}