Remove specific characters from a string in Javascript

I am creating a form to lookup the details of a support request in our call logging system.

Call references are assigned a number like F0123456 which is what the user would enter, but the record in the database would be 123456. I have the following code for collecting the data from the form before submitting it with jQuery ajax.

How would I strip out the leading F0 from the string if it exists?

$('#submit').click(function () {        
            
var rnum = $('input[name=rnum]');
var uname = $('input[name=uname]');

var url = 'rnum=' + rnum.val() + '&uname=' + uname.val();

Solution 1:

Simply replace it with nothing:

var string = 'F0123456'; // just an example
string.replace(/^F0+/i, ''); '123456'

Solution 2:

Honestly I think this probably the most concise and least confusing, but maybe that is just me:

str = "F0123456";
str.replace("f0", "");

Dont even go the regular expression route and simply do a straight replace.

Solution 3:

Another way to do it:

rnum = rnum.split("F0").pop()

It splits the string into two: ["", "123456"], then selects the last element.

Solution 4:

Regexp solution:

ref = ref.replace(/^F0/, "");

plain solution:

if (ref.substr(0, 2) == "F0")
     ref = ref.substr(2);