"node --harmony ." doesn't work. The error I get is put in the comment of index.js

dice_roll.js

const commando = require('discord.js-commando');

class DiceRollCommand extends commando.Command {
    contructor(client) {
        super(client, {
            name: 'roll',
            group: 'random',
            memberName: 'roll',
            description: 'Rolls a dice'
        });
    }

    async run(message, args) {
            var roll = Math.floor(Math.random() * 6) + 1;
            message.reply("You rolled a " + roll);
    }
}

module.exports = DiceRollCommand;

index.js

const commando = require('discord.js-commando');
const bot = new commando.Client();

bot.registry.registerGroup('random', 'Random');
bot.registry.registerDefaults();
bot.registry.registerCommandsIn(__dirname + "/commands");

bot.login('mybotnodehere'); 


/*
C:\Users\Hakej\Desktop\Mizin Bot\commands\random\dice_roll.js:5
        super(client, {
        ^^^^^
SyntaxError: 'super' keyword unexpected here
    at Object.exports.runInThisContext (vm.js:78:16)
    at Module._compile (module.js:543:28)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at require (internal/module.js:20:19)
    at C:\Users\Hakej\Desktop\Mizin Bot\node_modules\require-all\index.js:52:46
    at Array.forEach (native)
    at requireAll (C:\Users\Hakej\Desktop\Mizin Bot\node_modules\require-all\index.js:34:9)
*/