substring.js

function finder(filename, string){
  for(var ifilename = 0, istring = 0;ifilename<filename.length;ifilename++){
    var cstring = string[istring],
        cfilename = filename[ifilename];
    // console.log(i, cstring, cfilename);

    if(cstring == cfilename){
      istring++;
      if(istring == string.length)
        return true;
    }
  }
  return false;
}