!message.member.hasPermission code example

Example 1: if member has role discord.js

let allowedRole = message.guild.roles.find("name", "rolename");
    if (message.member.roles.has(allowedRole.id) {
        // allowed access to command
    } else {
       // not allowed access
    })

Example 2: discord.js v12 how to set owner commands

// First we use guild.members.fetch to make sure all members are cached
<message>.guild.members.fetch().then(fetchedMembers => {
	const totalOnline = fetchedMembers.filter(member => member.presence.status === 'online');
	// We now have a collection with all online member objects in the totalOnline variable
	<message>.channel.send(`There are currently ${totalOnline.size} members online in this guild!`);
});