how to check for many servers a bot is in discord.js code example

Example 1: how to see in how many servers your discord bot is d.js

You need to use client.setActivity() and then use the client.guilds.cache.size value. 
For example:

client.setActivity(`Currently in ${client.guilds.cache.size} servers`);

Example 2: see how many servers your discord bot is in

len(client.servers)