ES2015 - Proxy - Property set validation

gistfile1.js

//Validation Proxy example
let handler = {
  //Intercept any object property set operation
  set: function(obj, prop, value){
    if(prop === 'age' && !Number.isInteger(value)){
      throw new TypeError('Age should be an integer number');
    }
    obj[prop] = value;
  }
}

let target = {
  age: 25
};
let proxy = new Proxy(target, handler);


proxy.age = 'foo';