object.js

alert = console.log

var o = {
  a: 7,
  get b() { 
    return this.a + 1;
  },
  set c(x) {
    this.a = x / 2;
  }
};

console.log(o.a); // 7
console.log(o.b); // 8
o.c = 50;
console.log(o.a); // 25

var d = Date.prototype;
Object.defineProperty(d, 'year', {
  get: function() { return this.getFullYear(); },
  set: function(y) { this.setFullYear(y); }
});

var now = new Date();
console.log(now.year); // 2000
now.year = 2001; // 987617605170
console.log(now);
// Wed Apr 18 11:13:25 GMT-0700 (Pacific Daylight Time) 2001

var o = { a: 0 };

Object.defineProperties(o, {
    'b': { get: function() { return this.a + 1; } },
    'c': { set: function(x) { this.a = x / 2; } }
});

o.c = 10; // Runs the setter, which assigns 10 / 2 (5) to the 'a' property
console.log(o.b); // Runs the getter, which yields a + 1 or 6

// Creates a new object, myobj, with two properties, a and b.
var myobj = new Object;
myobj.a = 5;
myobj.b = 12;

// Removes the a property, leaving myobj with only the b property.
delete myobj.a;
console.log ('a' in myobj); // output: "false"

{
  let user = {
    name: "John",
    age: 30
  };

  alert(Object.keys(user))
  alert(Object.values(user))
  alert(Object.entries(user))
  // loop over values
  for (let value of Object.values(user)) {
    alert(value); // John, then 30
  }
}

{
  let prices = {
    banana: 1,
    orange: 2,
    meat: 4,
  };

  let doublePrices = Object.fromEntries(
    // convert to array, map, and then fromEntries gives back the object
    Object.entries(prices).map(([key, value]) => [key, value * 2])
  );

  alert(doublePrices.meat); // 8
}