Requisitos: Dado um Schema inicial simples, aplicar funções de transformação em campos definidos pelo usuário.

test.js

'use strict';

var Schema = {
    name: {
        type: String
    },
    lastname: {
        type: String
    },
    avatar: {
        type: Number
    },
    birthday: {
        type: Date
    }
};

/* código de intra-estrutura code */
class Action {
	
    constructor(propName, action){
        this.propName = propName;
		this.do = action;
    }
   
    static for(propName, action){
        return new Action(propName, action);
    }
}

class Mediator {
	
    constructor(schema){
		var self = this;
		
        self.itens = new Map();
        self.completedList = new Map();
		
        for(let prop in schema)
            self.itens.set(prop, Action.for(prop, function(value) {
                self.completedList.has(prop) && self.completedList.get(prop).call(value, value);
				return value;
            }));

    }
    
    onComplete(propName, callback){
        this.completedList.set(propName, callback)
    }
    
    apply(obj){
        for(let prop in obj){		
		this.itens.has(prop) && this.itens.get(prop).do.call(obj, obj[prop]);
		}
    }
    static for(schema, actions){
        var mediator = new Mediator(schema);      

		actions.reverse().forEach( (item) =>{
         
		   let cb = mediator.itens.get(item.propName);          	   
		   
           mediator.itens.set(item.propName, Action.for(item.propName, function(param){
			   let holder = item.do.call(param, param);
                return cb.do.call(holder, holder);  
           }));
		   
        });
		
		return mediator;
    }
}

/* código do cliente */


var actions = [
    Action.for('name', String.prototype.toUpperCase),
    Action.for('name', str => str.substring(0,5))
];

var mediator = Mediator.for(Schema, actions);

mediator.onComplete('name', function(value){
   console.log(value); 
});

mediator.onComplete('birthday', function(value){
   console.log(value); 
});

mediator.apply({
    "name": "Cleiton",
	"lastname":"Gomes",
	"birthday": new Date(1986, 2, 13)
});