Yes, React JS creates a virtual DOM (Document Object Model) in memory. The virtual DOM is a lightweight, abstract representation of the actual DOM that exists in the browser, and it is used by React to improve the performance and efficiency of web applications. Let me explain in detail:
When a React component is rendered, it creates a virtual DOM tree that mirrors the structure of the actual DOM tree. Each element in the virtual DOM is represented by a JavaScript object that contains information about the element’s type, properties, and children.
The virtual DOM is used to compare the previous and current states of a component and determine the minimum set of changes needed to update the actual DOM. This process is known as reconciliation, and it involves comparing the old virtual DOM tree with the new virtual DOM tree and calculating the differences between them.
By using the virtual DOM, React can update the actual DOM more efficiently and avoid unnecessary re-renders of components. Instead of updating the entire DOM tree, React only updates the parts of the tree that have changed, resulting in faster and more responsive web applications.
For example, when the a button is clicked in a React JS app, the handleClick function updates the count state by calling the function let’s say ‘setCount’.
When setCount is called, React creates a new virtual DOM tree that represents the updated UI. React then compares the new virtual DOM tree with the old virtual DOM tree to determine the minimum set of changes needed to update the actual DOM. In this case, React only needs to update the text of the h1 element to reflect the new count value, so it updates only that part of the actual DOM.
In conclusion, React JS creates a virtual DOM in memory to improve the performance and efficiency of web applications. The virtual DOM allows React to update the actual DOM more efficiently and avoid unnecessary re-renders of components, resulting in faster and more responsive web applications.