Count number of matches.

I am adding some code on to an existing script. What i am trying to do is match the files against files located as a back up on the server. Verifying that they are all there. I have been able to match them but now I want to count how many matches i have. This should be easy but I am confused.

for ( i = 0; i < count; i++ ) {
       
         file = doc.visibleThumbnails.spec.toSource();
         f =doc.visibleThumbnails.name.slice(0,10);
        pageImage =doc.visibleThumbnails.name;
        extractName=boot.name;
        var myMatch=0;
    for (var j = 0; j < boot.length; j++) {
   
        if((pageImage.match ( boot.name))){myMatch=myMatch++; }         
        }
    
    alert(myMatch);
}

I thought I could just asign ++ to a var but its not working.