tl;dr

1. In ECMAScript 2017, just call Object.entries(yourObj).
2. In ECMAScript 2015, it is possible with Maps.
3. In ECMAScript 5, it is not possible.

ECMAScript 2017

ECMAScript 2017 introduced a new Object.entries function. You can use this to iterate the object as you wanted.

'use strict';

const object = {'a': 1, 'b': 2, 'c' : 3};

for (const [key, value] of Object.entries(object)) {
  console.log(key, value);
}

Output

a 1
b 2
c 3

ECMAScript 2015

In ECMAScript 2015, there is not Object.entries but you can use Map objects instead and iterate over them with Map.prototype.entries. Quoting the example from that page,

var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

var mapIter = myMap.entries();

console.log(mapIter.next().value); // ["0", "foo"]
console.log(mapIter.next().value); // [1, "bar"]
console.log(mapIter.next().value); // [Object, "baz"]

Or iterate with for..of, like this

'use strict';

var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

for (const entry of myMap.entries()) {
  console.log(entry);
}

Output

[ '0', 'foo' ]
[ 1, 'bar' ]
[ {}, 'baz' ]

Or

for (const [key, value] of myMap.entries()) {
  console.log(key, value);
}

Output

0 foo
1 bar
{} baz

ECMAScript 5:

No, it's not possible with objects.

You should either iterate with for..in, or Object.keys, like this

for (var key in dictionary) {
    // check if the property/key is defined in the object itself, not in parent
    if (dictionary.hasOwnProperty(key)) {           
        console.log(key, dictionary[key]);
    }
}

Note: The if condition above is necessary only if you want to iterate over the properties which are the dictionary object's very own. Because for..in will iterate through all the inherited enumerable properties.

Or

Object.keys(dictionary).forEach(function(key) {
    console.log(key, dictionary[key]);
});

Iterating over properties requires this additional hasOwnProperty check:

for (var prop in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, prop)) {
        // do stuff
    }
}

It's necessary because an object's prototype contains additional properties for the object which are technically part of the object. These additional properties are inherited from the base object class, but are still properties of obj.

hasOwnProperty simply checks to see if this is a property specific to this class, and not one inherited from the base class.

It's also possible to call hasOwnProperty through the object itself:

if (obj.hasOwnProperty(prop)) {
    // do stuff
}

But this will fail if the object has an unrelated field with the same name:

var obj = { foo: 42, hasOwnProperty: 'lol' };
obj.hasOwnProperty('foo');  // TypeError: hasOwnProperty is not a function

That's why it's safer to call it through Object.prototype instead:

var obj = { foo: 42, hasOwnProperty: 'lol' };
Object.prototype.hasOwnProperty.call(obj, 'foo');  // true