here,try this:
client.on('message', message =>{
if(message.content.startsWith(prefix) ||message.author.bot) return;
const args = message.content.slice(prefix.lenght).split(/+/);
const command = args.shift().toLowerCase();
if(command === 'blackhumour'){
message.channel.send('What is the difference between a kid and a bowling ball? when you put your fingers in one it doesnt scream');
} else if(command === 'sex'){
message.channel.send('no you fucking pervert');
}
});