Differencies: for of, for in, for in hasOwnProperty. arrays and objects.

iterations.es6

(()=>{'use strict';

let iterable = [3, 5, 7];
iterable.foo = "hello";
console.log('# iterable', iterable)

console.log('## access prop in array')
console.log(iterable.foo) // hello

console.log('## for in arr')
for (let i in iterable) {
  console.log(i); // logs keys: "0", "1", "2", "foo"
}

console.log('## for of arr')
for (let i of iterable) {
  console.log(i); // logs 3, 5, 7
}

console.log('## for of object')
// for (let i of {a:1,b:2}){console.log(i)} // error
console.error('error')

let object = {foo:'bar', foo1: 'bar1'};
object.__proto__ = {baz:'qux'}
console.log('\n# object', object);

console.log('## access proto of object')
console.log(object.baz) // logs qux

console.log('## for in object')
for (let i in object) {
  console.log(i); // logs keys: "foo", "foo1", "baz"
}
console.log('## for hasOwnProperty in object')
for (let i in object) { if(! object.hasOwnProperty(i)) {continue;}
  console.log(i); // logs keys: "foo", "foo1"
}

})();