function doGet(){
    var template = HtmlService.createTemplateFromFile('index');
    template.action = ScriptApp.getService().getUrl();
    return template.evaluate();
}

function doPost(e) {
    //all logic
    return ContentService.createTextOutput("Thank you");
}

function doPost(e) {
    //all logic
    return ContentService.createTextOutput(JSON.stringify(e.parameter));
}

function doPost(e) {
    //all logic
    var htmlBody = "<h1>Thank you.</h1>";
    return HtmlService.createHtmlOutput(htmlBody);
}

function doPost(e) {
    //all logic
    var template = HtmlService.createTemplateFromFile('Thanks');
    return template.evaluate();
}