如何使用Google应用脚本检查是否已经存在插入到Google表格中的数据？

Question

在电子表格中插入新行时，我要检查电子表格中是否已经存在该数据。而且我还想为插入表中的每一行自动增加一列。

function insert_value(request, sheet) 
{

    var firstname = request.parameter.firstname;
    var lastname = request.parameter.lastname;
    var mobileno = request.parameter.mobileno;
    var emailid = request.parameter.emailid;
    var password = request.parameter.password;

    var flag = 1;
    var lr = sheet.getLastRow();
    for (var i = 1; i <= lr; i++) 
    {
        var mobileno1 = sheet.getRange(i, 2).getValue();
        var emailid1 = sheet.getRange(i, 2).getValue();
        if ((mobileno1 == mobileno)||(emailid1 == emailid))
        {
            flag = 0;
            var result = "User already exists..";
        }
    }
    //add new row with recieved parameter from client
    if (flag == 1) 
    {    
        var sno=sno+1;
        var lockerno=lockerno+1;
        var d = new Date();
        var currentTime = d.toLocaleString();
        var rowData = sheet.appendRow([sno,firstname,lastname,mobileno,emailid,password,lockerno]);
        var result = "Registered successful";
    }