Cant Add Property _tracking Object Is Not Extensible

Encountering an error message that says "Cannot add property _tracking, object is not extensible" can be quite frustrating for developers, especially when trying to add properties to an object in their code. In this article, we'll dive into what this error means and explore some possible solutions to resolve it.

When you see the error message "Cannot add property _tracking, object is not extensible," it usually indicates that you are attempting to add a new property to an object that has been defined as non-extensible. In JavaScript, objects have a property called "extensible" that determines whether new properties can be added to the object or not. Once an object is marked as non-extensible, any attempts to add new properties will result in this error.

To check if an object is extensible or not, you can use the Object.isExtensible() method provided by JavaScript. This method returns a boolean value indicating whether the object is extensible or not. If the object is not extensible, you will need to make it extensible before adding new properties.

Here's an example of how you can check the extensibility of an object:

let myObject = {
  name: 'John',
  age: 30
};

console.log(Object.isExtensible(myObject)); // Outputs true

Object.preventExtensions(myObject); // Makes the object non-extensible

console.log(Object.isExtensible(myObject)); // Outputs false

In the example above, we first create an object called myObject with some properties. We then check if the object is extensible using Object.isExtensible(), which returns true initially. After that, we use Object.preventExtensions() to make the object non-extensible, and the subsequent call to Object.isExtensible() returns false.

Now that you understand the root cause of the error message, let's discuss some strategies to overcome it:

1. Check Extensibility: Before adding new properties to an object, always check if the object is extensible using Object.isExtensible(). If it's not extensible, consider making it extensible first.

2. Make Object Extensible: If you encounter the "Cannot add property" error, and the object is non-extensible, you can use Object.preventExtensions() to make it extensible before adding new properties.

3. Use Object.defineProperty(): Another approach is to use Object.defineProperty() to define new properties on an object explicitly. This method allows you to define property attributes such as configurable, enumerable, and value.

let myObject = {
  name: 'John'
};

Object.defineProperty(myObject, 'age', {
  value: 30,
  writable: true,
  enumerable: true,
  configurable: true
});

console.log(myObject); // Outputs { name: 'John', age: 30 }

By following these tips and understanding how object extensibility works in JavaScript, you can effectively address the "Cannot add property _tracking, object is not extensible" error and enhance your coding experience. Remember to always handle object extensibility appropriately to avoid encountering this issue in your projects.

Happy coding!