woomy/src/commands/calculate.js

var allowed = ["+", "-", "*", "/", "(", ")", " "];
exports.run = (client, message, args) => {
	let exercise = args.join(" ");
	
  if (!exercise) {
    return message.channel.send(
      `<:error:466995152976871434> No equation provided. Usage :\`${client.commands.get(`calculate`).help.usage}\``
    );
  }
  
	for (var i = 0; i < exercise.length; i++) {
		let c = exercise.charAt(i);
		let found = allowed.find((element) => element === c);
		
		if(c == "0") found = true;
		if(!(Number(c) || found))
		{
			return message.channel.send(
			  `<:error:466995152976871434> Invalid equation. Please use \`*\` for multiplication and \`/\` for division!`
			);
		}
	}
  
  let result = (new Function( 'return ' + exercise )());

  message.channel.send(`\`RESULT:\`\n\`\`\`${result}\`\`\``);
};

exports.conf = {
  enabled: true,
  guildOnly: false,
  aliases: ["calc", "math"],
  permLevel: "User",
  requiredPerms: []
};

exports.help = {
  name: "calculate",
  category: "Utility",
  description: "Solves basic mathematical equations.",
  usage: "calculate [equation]"
};