There is one caveat to the key/value loop that Ian mentioned. If it is possible that the Objects may have attributes attached to their Prototype, and when you use the in operator, these attributes will be included. So you will want to make sure that the key is an attribute of your instance, and not of the prototype. Older IEs are known for having indexof(v) show up as a key.
for (const key in myDictionary) {
if (myDictionary.hasOwnProperty(key)) {
let value = myDictionary[key];
}
}