when do you use Object.defineProperty()

Question

I\'m wondering when I should use

Object.defineProperty

to create new properties for an object. I\'m aware that I\'m able to set things lik

Answer 1

A really good reason for using Object.defineProperty is that it lets you loop through a function in an object as a computed property, which executes the function instead of returning the function's body.

For example:

var myObj = {};

myObj.width = 20;
myObj.height = 20;

Object.defineProperty(myObj, 'area', {
    get: function() {
        return this.width*this.height;
    },
    enumerable: true
});

for (var key in myObj) {
  if (myObj.hasOwnProperty(key)) {
    console.log(key + " -> " + myObj[key]);
  }
}
//width -> 20, height -> 20, area -> 400

Versus adding the function as a property to an object literal:

var myObj = {};

myObj.width = 20;
myObj.height = 20;

myObj.area = function() {
       return this.width*this.height;
    };

for (var key in myObj) {
  if (myObj.hasOwnProperty(key)) {
    console.log(key + " -> " + myObj[key]);
  }
}
// width -> 20, height -> 20, area -> function() { return this.width*this.height;}

Make sure you set the enumerable property to true in order to loop through it.