How to use sjcl.js for ECDH and Shared Key Exchange

sjcl-shared-key-debug.js

function User(username, key_pair){
  this.username = username;
  
  /* If no existing keys generate them */
  if(!key_pair){
    this.keys = sjcl.ecc.elGamal.generateKeys(192,0);  
  }else{
    this.keys = key_pair
  }
  
  /* Stores Username -> Pub Key */
  this.session_keys = {};
  
  /* Publicly Transfer The Users DH public key to the recipient */
  this.send_key_to_user = function(user_recipient){
    
    log("User: "+this.username+" sending key to "+user_recipient.username);
    user_recipient.recieve_key(this.keys.pub, this.username);
    
  }
  
  /* Recieve the sender's DH public key and store it */
  this.recieve_key = function(key,username){
    
    log("User: "+this.username+" recieved key from "+username);
    this.session_keys[username] = key;
    
  }
  
  /* 
    Computes the DH shared key from User's sec (secret key) 
    and the recipientes pre shared pub key 
  */
  this.get_shared_key = function(username){
    return this.keys.sec.dh(this.session_keys[username])
  }
  
  /* Assume the user has the recipients username & key */
  this.send_message = function(user_recipient, clear_text){
    
    log( "User: " + this.username + " sending message to " + user_recipient.username,"\""+clear_text+"\"" );
    
    var shared_key = this.get_shared_key(user_recipient.username);
    log("User: "+this.username+" and User: "+user_recipient.username+" Have the shared key:",shared_key);
    
    /* Encrypt the clear_text message using the shared session key */
    var cipher_text = sjcl.encrypt(shared_key, clear_text);
    log( user_recipient.read_message(cipher_text,this.username) );
    
    return cipher_text;
    
  }
  
  /* 
     Gets the user's shared key using their username
     Decrypts the text using that key
  */
  this.read_message = function(plain_text, username){
    
    log("User: "+ this.username +" read a message from " + username+" With encrypted content: ",plain_text);
    var shared_key = this.get_shared_key(username)
    
    var message_clear_text = sjcl.decrypt(shared_key,plain_text);
    log("The message in clear text read:",message_clear_text)
  }
}

var log = (...args) => args.forEach( a => console.log(a) )

var Bob = new User('Bob');
var Alice = new User('Alice');

Bob.send_key_to_user(Alice);

Alice.send_key_to_user(Bob);

Bob.send_message(Alice, "I wonder if Eve can hear us");

Alice.send_message(Bob, "I hope not, I hate Eve!");

sjcl-shared-key.js

function User(username, key_pair){
  this.username = username;
  
  /* If no existing keys generate them */
  if(!key_pair){
    this.keys = sjcl.ecc.elGamal.generateKeys(192,0);  
  }else{
    this.keys = key_pair
  }
  
  /* Stores Username -> Pub Key */
  this.session_keys = {};
  
  /* Publicly Transfer The Users DH public key to the recipient */
  this.send_key_to_user = function(user_recipient){
    user_recipient.recieve_key(this.keys.pub, this.username);
  }
  
  /* Recieve the sender's DH public key and store it */
  this.recieve_key = function(key,username){
    this.session_keys[username] = key;
  }
  
  /* 
    Computes the DH shared key from User's sec (secret key) 
    and the recipientes pre shared pub key 
  */
  this.get_shared_key = function(username){
    return this.keys.sec.dh(this.session_keys[username])
  }
  
  /* Assume the user has the recipients username & key */
  this.send_message = function(user_recipient, clear_text){
    var shared_key = this.get_shared_key(user_recipient.username);
    
    /* Encrypt the clear_text message using the shared session key */
    return sjcl.encrypt(shared_key, clear_text);
  }
  
  /* 
     Gets the user's shared key using their username
     Decrypts the text using that key
  */
  this.read_message = function(plain_text, username){
    var shared_key = this.get_shared_key(username)
    return sjcl.decrypt(shared_key,plain_text);
  }
}

var Bob = new User('Bob');
var Alice = new User('Alice');

Bob.send_key_to_user(Alice);

Alice.send_key_to_user(Bob);

Bob.send_message(Alice, "I wonder if Eve can hear us");

Alice.send_message(Bob, "I hope not, I hate Eve!");

Lemme know if I did something incorrectly... The sjcl library is a bit confusing.
sjcl.js Crypto Library