Remove all characters after last - but only if after - has four characters

I have a string which could contain several different values, among them are.

EDITED for clarity: var test could equal FW21002-185 or FW21002-181-0001 or abcdefg or 245-453-654 or FW21002-181-00012

I would like to remove all characters after and including the last - only if that string contains four characters after the last dash. So in the above strings examples, the only one that should be changed is the second one to "FW21002-181" All others would remain as they are开发者_如何学编程.

How would I do this in JavaScript. Regex is ok as well. Thanks.

A regex to do this would be

var chopped = test.replace(/-[^-]{4,}$/, '-');

(assuming you want that "-" at the end). (Oh also this is intended to match 4 or more trailing characters - if you want exactly four, just get rid of the comma in {4,}.)

No regex required:

var str = ...,
    pos = str.lastIndexOf('-');

if (pos > -1 && pos == str.length - 5)
  str = str.substring(0, pos);

If you don't want to use a regex:

function removeLongSuffix(var str)
{
    var tokens = str.split('-'),
        last = tokens[tokens.length-1];
        if (last.length > 3)
        {
            return tokens.slice(0,-1).join('-');
        }
        return str;
}