Aswer

Check the callback or promise result to redeemKey.

Thank you but.. i'm new to this stuff and I searched everywhere to find an example...

Can you plase help me with an small example 

Thank you for your time.

Hi, im new to this and i don't know how to check if the key is valid or invalid..

This is the code 

client.on("friendMessage", function (steamID, message) {
    if (steamID == AdminID && message.indexOf('!key') == 0) {
        var GetKey = message.replace('!key ', '');
        client.redeemKey(GetKey);
        client.chatMessage(steamID, "Key activated: " + GetKey);
    }
});

Thanks