reaction collector filter code example

Example: await message discord.js

message.channel.awaitMessages(m => m.author.id == message.author.id,
                            {max: 1, time: 30000}).then(collected => {
                                    // only accept messages by the user who sent the command
                                    // accept only 1 message, and return the promise after 30000ms = 30s

                                    // first (and, in this case, only) message of the collection
                                    if (collected.first().content.toLowerCase() == 'yes') {
                                            message.reply('Shutting down...');
                                            client.destroy();
                                    }

                                    else
                                            message.reply('Operation canceled.');      
                            }).catch(() => {
                                    message.reply('No answer after 30 seconds, operation canceled.');
                            });