Interface example in Javascript

Interface.js

//  INTERFACE "X"
var X = {
   share: function(clientEmail, email ){}
};
// LIB "A"
var A = {
    type: 'facebook'   
};
// LIB "B"
var B = {
    type: 'twitter'   
};

//  CLASS "XA"
var XA = function(A) {
    this.A = A;
};
XA.prototype = Object.create(X);
XA.prototype.share = function(clientEmail, email ){
    console.log('client: '+clientEmail + ', email: '+email+', type: '+A.type);
};

//  CLASS "XB"
var XB = function() {
    this.B = B;
};
XB.prototype = Object.create(X);
XB.prototype.share = function(clientEmail, email ){
    console.log('client: '+clientEmail + ', email: '+email+', type: '+B.type);
};

var xa = new XA(A);
var xb = new XB(B);

console.log(xb.share('this is XB content', '[email protected]'));
console.log(xa.share('this is XA content', '[email protected]'));