Encrypting form data with RSA at client side with javascript

Question

I want to encrpyt my password and username from client side and decrypt it at server side(Asp.net core) with RSA(Or any other asymmetric algorithms). I am gonna send public key from server side so I don't need to create a public key at client side only need to encrypt it.

I am trying something like this..

var encrypt = new JSEncrypt();
      encrypt.setPublicKey($('#pubkey').val());
      var encrypted = encrypt.encrypt($('#input').val());

but it says JSEncrypt is not defined normally. But I don't know how to include this propery at my code. https://github.com/travist/jsencrypt in here there is a good explanation but still I couldn't manage to do it. Also I really need a simple thing for just encryption with a known public key.

Edit 1: I am using https already but I still need to do it unfortunately.