Object.getOwnPropertyNames

Object.getOwnPropertyNames(obj)

var arr = ['a', 'b', 'c'];
console.log(Object.getOwnPropertyNames(arr).sort() 
// logs ["0", "1", "2", "length"]

// Array-like object
var obj = { 0: 'a', 1: 'b', 2: 'c' };
console.log(Object.getOwnPropertyNames(obj).sort() 
// logs ["0", "1", "2"]

// Logging property names and values using Array.forEach
Object.getOwnPropertyNames(obj).forEach(
  function (val, idx, array) {
    console.log(val + ' -> ' + obj[val]
  }

// logs
// 0 -> a
// 1 -> b
// 2 -> c

// non-enumerable property
var my_obj = Object.create{}, {
  getFoo: {
    value: function() { return this.foo; },
    enumerable: false
  }
}
my_obj.foo = 1;

console.log(Object.getOwnPropertyNames(my_obj).sort() 
// logs ["foo", "getFoo"]

function ParentClass() {}
ParentClass.prototype.inheritedMethod = function() {};

function ChildClass() {
  this.prop = 5;
  this.method = function() {};
}
ChildClass.prototype = new ParentClass;
ChildClass.prototype.prototypeMethod = function() {};

console.log(
  Object.getOwnPropertyNames(
    new ChildClass() // ["prop", "method"]
  )

var target = myObject;
var enum_and_nonenum = Object.getOwnPropertyNames(target
var enum_only = Object.keys(target
var nonenum_only = enum_and_nonenum.filter(function(key) {
  var indexInEnum = enum_only.indexOf(key
  if (indexInEnum == -1) {
    // Not found in enum_only keys,
    // meaning that the key is non-enumerable,
    // so return true so we keep this in the filter
    return true;
  } else {
    return false;
  }
}

console.log(nonenum_only

Object.getOwnPropertyNames('foo'
// TypeError: "foo" is not an object (ES5 code)

Object.getOwnPropertyNames('foo'
// ["0", "1", "2", "length"]  (ES2015 code)