Unlocking the Power of Object Sealing in JavaScript
What is Object Sealing?
In JavaScript, object sealing is a powerful feature that allows you to restrict modifications to an object’s properties. But how do you know if an object is sealed or not? That’s where the Object.isSealed() method comes in.
The Syntax of isSealed()
The isSealed() method is a static method that takes in an object as a parameter. The syntax is simple: Object.isSealed(obj). This method returns a Boolean value indicating whether the object is sealed or not.
Understanding the Return Value
The isSealed() method returns true if the object is sealed and false otherwise. But what does it mean for an object to be sealed? A sealed object is not extensible, meaning you can’t add new properties or delete existing ones. However, a sealed object may still be writable, depending on its properties before sealing.
Real-World Examples
Let’s take a look at some examples to illustrate how isSealed() works.
Example 1: The Empty Object
Creating an empty object and checking its seal status returns false, as expected.
Example 2: The Non-Empty Object
Things get interesting when we create an object with properties. Simply using preventExtensions() doesn’t guarantee sealing. We need to ensure all properties are non-configurable. In this case, isSealed() returns false until we set the configurable flag to false using defineProperty().
Example 3: The Power of seal()
Using the seal() method always ensures an object is sealed. In this example, isSealed() returns true after sealing the object.
The Takeaway
In JavaScript, Object.isSealed() is a crucial method for determining whether an object is sealed or not. By understanding how it works and when to use it, you can write more robust and efficient code. Remember, sealing an object is not just about preventing extensions, but also about ensuring all properties are non-configurable.