I am looking at a sample from mozilla documents about JS and here is this snippet that shows that For..of prints 3, 5, 7, but why not "hello"?
let arr = [3, 5, 7];
arr.foo = "hello";
for (let i in arr) {
console.log(i); // logs "0", "1", "2", "foo"
}
for (let i of arr) {
console.log(i); // logs "3", "5", "7" ?????
}