gistfile1.js

function CSV(how, exportObjectSize, docName){
        this.how = how;                     // append is default
        this.exportSize = exportObjectSize; // yes/no
        this.docName = docName;             // file name to export to
 } 

CSV.prototype.export = function(input) {
    var inputFolder = Folder.selectDialog();
    var csv = new File(inputFolder+"/"+this.docName+".csv");
          // open text again
          switch(this.how) {
            case "overwrite": csv.open("w"); break; //overwrite last setting
            case "append": csv.open("a"); break; //append to file
            default: csv.open("a");// set default to append to file
          }
          csv.writeln(input); // write your new data to it
          csv.close(); // close csv
}


var newExport = new WuCSV("append", "yes", "sizes");
newExport.exportMe(firstSymbol.getWidthHeight());