Question

I have a javascript function that forces a space after every 26 letters

function nospaces(t)    
{
    if(t.value.match(/\S{27}/g))
    {    
        //alert('Sorry, you can not enter a word more than 26 characters long');
        t.value[5]=t.value.replace(/\S{27}/g,'');
    }
}

Now i want that every 27th letter that user enter instead of space should replaced by space

Answer 1

Make smart use of regex groups, if \S{26} is followed by a \S replace the whole match with the first group followed by a space;

var foo = 'abcdefghijklmnopqrstuvwxyzab'.replace(/(\S{26})(\S)/, '$1 ');
gives:
abcdefghijklmnopqrstuvwxyz b