xiao/commands/random/math.js

const { Command } = require('discord.js-commando');
const math = require('mathjs');

module.exports = class MathCommand extends Command {
    constructor(client) {
        super(client, {
            name: 'math',
            group: 'random',
            memberName: 'math',
            description: 'Does math.',
            args: [
                {
                    key: 'expression',
                    prompt: 'What do you want to answer?',
                    type: 'string'
                }
            ]
        });
    }

    run(msg, args) {
        const { expression } = args;
        try {
            const solved = math.eval(expression);
            return msg.say(solved)
                .catch(() => msg.say('Invalid statement.'));
        } catch(err) {
            return msg.say('Invalid statement.');
        }
    }
};