Fixing null initial value in BehaviourSubject

Introduction

When working with RxJS, it is common to use the `BehaviorSubject` class to represent a value that changes over time. However, when initializing a `BehaviorSubject`, it is possible to encounter the issue of a `null` initial value, which can cause problems in some scenarios. In this article, we will explore how to fix this issue and ensure that our `BehaviorSubject` initializes with a proper initial value.

The Issue

The issue of a `null` initial value in a `BehaviorSubject` can occur when we create a new instance of the class without providing an initial value. For example:

const subject = new BehaviorSubject();

In this case, the `subject` instance will be created with a `null` initial value, which can cause problems when subscribing to it or using it in other parts of our code.

The Solution

To fix this issue, we need to provide an initial value when creating a new instance of `BehaviorSubject`. For example, if we want to initialize our `subject` instance with the value `0`, we can do the following:

const subject = new BehaviorSubject(0);

In this case, the `subject` instance will be created with an initial value of `0`, which will prevent any issues related to `null` values.

If we don't know the initial value of our `BehaviorSubject` at the time of creation, we can use a different approach to ensure that it always has a proper initial value. We can create a function that returns a default value, and use that function as the initial value of our `BehaviorSubject`. For example:

function getDefault() {
  return 0;
}

const subject = new BehaviorSubject(getDefault());

In this case, the `subject` instance will be created with the default value returned by the `getDefault()` function, which can be updated later if needed.

Conclusion

In this article, we have explored the issue of a `null` initial value in `BehaviorSubject`, and how to fix it by providing a proper initial value when creating a new instance. By following these guidelines, we can ensure that our `BehaviorSubject` instances always have a valid initial value, and avoid any issues related to `null` values.