Easy Google Apps Script Secret Santa code given a spreadsheet with names in the B column and emails in the C column

code.js

var ss = SpreadsheetApp.getActiveSpreadsheet(); // this is meant to run inline google appsscript - you'll have to use a different get method if you don't want that
var sheet = ss.getSheets()[0]; // assumes sheet 1

var names = sheet.getRange(2,2,sheet.getLastRow()-1,2).getValues(); 
Logger.log(names);


if (names.length % 2 != 0) {
    //alert("You must have an even number of names. You currently have " + names.length + " names.");
} else {
    var arr1 = names.slice(), // copy array
        arr2 = names.slice(); // copy array again

    arr1.sort(function() { return 0.5 - Math.random();}); // shuffle arrays
    arr2.sort(function() { return 0.5 - Math.random();});

    while (arr1.length) {
        var name1 = arr1.pop(), // get the last value of arr1
            name2 = arr2[0] == name1 ? arr2.pop() : arr2.shift();
            //        ^^ if the first value is the same as name1, 
            //           get the last value, otherwise get the first

     //   Logger.log(name1[1] + ' gets ' + name2[1]);
      var message = "This is an autogenerated email. Your Secret Santa match is: " + name2[0] + ". You can see their address/wish list here: <include link to spreadsheet>";
        GmailApp.sendEmail(name1[1], "Secret Santa", message);
    }
}