Message content toLowercase won't work?

[PicturemyBootyUpin3d]

My code:

client.on("message", message => {
  var lowercasemessage = message.content.toLowercase()
  if (lowercasemessage.includes("rappa 3000")) {
    message.channel.send("My fnaf rap! YO YO YO YO!", {files:["https://i.ytimg.com/vi/bwq2OLrNcwo/maxresdefault.jpg"]});
  }
});

[chessebuilderman]

It is toLowerCase not toLowercase