Store read dates

There’s an array of messages as in the previous task. The situation is similar.

          let messages = [
  {text: "Hello", from: "John"},
  {text: "How goes?", from: "John"},
  {text: "See you soon", from: "Alice"}
];
        

The question now is: which data structure you’d suggest to store the information: “when the message was read?”.

In the previous task we only needed to store the “yes/no” fact. Now we need to store the date, and it should only remain in memory until the message is garbage collected.

P.S. Dates can be stored as objects of built-in Date class, that we’ll cover later.

To store a date, we can use WeakMap:

          let messages = [
  {text: "Hello", from: "John"},
  {text: "How goes?", from: "John"},
  {text: "See you soon", from: "Alice"}
];

let readMap = new WeakMap();

readMap.set(messages[0], new Date(2017, 1, 1));
// Date object we'll study later
        