gistfile1.js

Object.prototype.foo = "bar";
Object.prototype.bar = "foo";

var test = {a: 1, b: 2, c: 3},
props = [], vals = [];
 
for (let prop in test) {
    props.push(prop);
}

for each (let val in test) {
    vals.push(val);
}

props.join(", ") === "a, b, c" && vals.join(", ") === "1, 2, 3";