getDirectMessages.js

var fs = require('fs');
var filename = './sendHistory.json';
var sendHistory;
try {
    JSON.parse(fs.readFileSync(filename));
} catch(err) {
    fs.writeFileSync(filename, JSON.stringify({data:[]})+'\n');
} finally {
    sendHistory = JSON.parse(fs.readFileSync(filename)).data;
}

var adminID = '123123123123123123'; // Your user ID here

function getDMs(dmChannel, delay) {
    setTimeout(function(){
        bot.getMessages({ channelID: dmChannel, limit: 100 }, function(err, messagesArray) {
            if(messagesArray.length === 0) return;
            messagesArray.reverse();
            var backlog = '__Message(s) from **' + messagesArray[0].author.username + '**__';
            var newMessages = 0;
            messagesArray.forEach(function(msg){
                if(msg.author.id === bot.id) return;
                if(sendHistory.indexOf(msg.id) >= 0) return;
                newMessages++;
                backlog += '\n' + msg.timestamp.substr(0,19) + ' ' + msg.content;
                sendHistory.push(msg.id);
            });
            if(newMessages === 0) return;
            bot.sendMessage({ to: adminID, message: backlog.substr(0, 2000) });
            fs.writeFileSync(filename, JSON.stringify({data:sendHistory})+'\n');
        });
    }, delay);
}
var dm = 0;
for(var dmKey in bot.directMessages) {
    if(!bot.directMessages.hasOwnProperty(dmKey)) continue;
    getDMs(dmKey, dm * 5000);
    dm++;
}