Observer APIs in JavaScript

Observer APIs in JavaScript

Observer APIs are very useful to detect changes in the applications. The following are the different types of observer APIs in JavaScript. Each type observes different things.

Observer#

Observer is an object which monitors or observes something continuously and it notifies after something is changed.

Observer APIs#

Observer APIs are very useful to detect changes in the applications. The following are the different types of observer APIs in JavaScript. Each type observes different things.

  1. MutationObserver
  2. IntersectionObserver
  3. ResizeObserver
  4. PerformanceObserver

Mutation Observer:#

Mutation Observer observes the DOM tree. It waits for the changes being made to the DOM.

Mutation Observer interface will notify us when the particular element’s attributes, text or contents changed. And also it monitors the child nodes whether it has been added or removed.

Mutation Observer Flow Diagram

Concepts:#

Key Concepts

These are the key concepts in Mutation Observer. It is not possible to read all these concepts and understand what they are doing. So, see some use cases and code examples in further and then you will have more clear understanding.

Use Cases:#

  1. Find immediate Undo & Redo values of DOM Elements.
  2. Remove unwanted DOM elements such as advertisements that are coming from third-party libraries.
  3. Resize DOM elements dynamically.
  4. Debugging third-party libraries are easier; we can track element creation and property changes.

We can use Mutation Observer wherever we want to track DOM Elements that is the core concept of Mutation Observer.

Now, I am going to take one use-case from the list and will explain it briefly. Try other use-cases on your own. It will be more interesting!

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