I am trying to make a discord.js avatar command, and the mentioning portion doesn't work correctly

Question

I have an avatar command in my discord bot. When the user uses h.avatar, it outputs their avatar, which works fine. Whenever they try to use h.avatar @user, nothing happens.
Here is my code:

 } if (message.content.startsWith(config.prefix + "avatar")) {
      if (!message.mentions.users.size) {
        const avatarAuthor = new Discord.RichEmbed()
      .setColor(0x333333)
      .setAuthor(message.author.username)
      .setImage(message.author.avatarURL)
        message.channel.send(avatarAuthor);
        let mention = message.mentions.members.first();
        const avatarMention = new Discord.RichEmbed()
        .setColor(0x333333)
        .setAuthor(mention.user.username)
        .setImage(mention.user.avatarURL)
        message.channel.send(avatarMention);

Answer 1

You have a check if (!message.mentions.users.size) { which makes the command run only if you do not mention somebody. You either need to use an else { in your code or do:

 if (message.content.startsWith(config.prefix + 'avatar')) {
    const user = message.mentions.users.first() || message.author;
    const avatarEmbed = new Discord.RichEmbed()
        .setColor(0x333333)
        .setAuthor(user.username)
        .setImage(user.avatarURL);
    message.channel.send(avatarEmbed);
}

The const user = message.mentions.users.first() || message.author; tries to get the user that was mentioned but if it does not find anyone it will use the author's used.

This can also be used like this:

if (!message.mentions.users.size) {
    message.channel.send('Nobody was mentioned');
    return;
}
// continue command here, after guard clause