ban.js

if (msg.member.hasPermission('BAN_MEMBERS')) {

        if (msg.mentions.members.size) {

            var member = msg.mentions.members.first();

            if (msg.args[0] == member.toString()) {

                if (member.bannable && (msg.member.highestRole.position > member.highestRole.position || msg.author.id == msg.guild.ownerID)) {

                    if (msg.args[2]) {

                        var purgeLength = (parseInt(msg.args[1])>0?parseInt(msg.args[1]):0);

                        msg.args.splice(0,2);

                        member.user.send(`You have been banned from \`${msg.guild.name}\` by \`${msg.author.tag}\` with the reason \`${msg.args.join(' ')}\``)

                        .then(()=>{

                            member.ban({reason: `Banned by ${msg.author.tag}, with reason: ${msg.args.join(' ')}.`,days: purgeLength}, purgeLength).then(()=>{

                                msg.channel.send(`Banned ${member.user.tag} successfully! (Reason: \`${msg.args.join(' ')}\`)`);

                            }).catch();

                        });

                    } else {

                        var purgeLength = (parseInt(msg.args[1])>0?parseInt(msg.args[1]):0);

                        member.user.send(`You have been banned from \`${msg.guild.name}\` by \`${msg.author.tag}\` with no reason specified.`)

                        .then(()=>{

                            member.ban({reason: `Banned by ${msg.author.tag}, with no reason.`,days: purgeLength}).then(()=>{

                                msg.channel.send(`Banned ${member.user.tag} successfully!`);

                            }).catch();

                        });

                    }

                } else {

                    msg.channel.send('Sorry! I cannot ban that user.');

                } 

            } else {

                msg.channel.send('The first argument must be a mention.');

            }

        } else {

            msg.channel.send(`Usage: \`${module.exports.usage(prefix)}\``);

        }

    } else {

        msg.channel.send('Sorry! You do not have permission to use this command!');

    }