How to add a key-value pair to a JavaScript object?

Hello everyone! I just started learning JavaScript and encountered this problem. I have an empty object that I created like this: ```javascript let myObject = {}; ``` Or, for example, I already have an object with some data: ```javascript let user = { name: "Anna", age: 25 }; ``` Now I need to dynamically add a new property to this object, for example, "email" or "isAdmin". I tried several methods, but I'm not sure which one is correct and which is better to use in different situations. Here's what I tried: 1. Simply assign a value using dot notation: `user.email = "anna@example.com";` 2. Use square brackets: `user["email"] = "anna@example.com";` 3. Use the `Object.assign()` method 4. Use the spread operator: `user = {...user,