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Store read dates

importance: 5

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, once again, should disappear if the message is gone.

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