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DOM Manipulation in JavaScript

Best Practices and Optimization for DOM Manipulation

DOM manipulation can significantly impact the performance of a web page. If not handled properly, it can lead to slowdowns, UI blocking, and a negative user experience. In this chapter, we will review some best practices and optimization techniques to improve efficiency and performance when manipulating the DOM.

Minimizing Reflows and Repaints

Every time you modify the DOM structure or the layout of an element, the browser performs a reflow (layout recalculation) and repaint (screen redraw). These processes can be costly in terms of performance.

Best Practices:

  • Avoid Multiple Changes: Try to make multiple changes at once instead of changing them one by one.

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  • Document Fragments: Use DocumentFragments to make multiple additions or changes to the DOM at once.

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  • Node Cloning: Clone a node, modify it, and then replace the original.

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Limiting DOM Accesses

Accessing the DOM is an expensive operation. Try to minimize the number of accesses by making all possible modifications in a single operation.

Caching Elements

Store references to DOM elements in variables to avoid repeated searches.

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Efficient Use of Selectors

Use efficient and specific selectors to minimize search time.

Using IDs and Specific Classes

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Avoid Direct Layout Manipulations

Some properties like offset, scroll, and client can force a reflow. Try to avoid using them repeatedly.

Example of Poor Use

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Using Variables

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Decoupling the DOM

Separate business logic from DOM manipulation and use frameworks or libraries that optimize these tasks, such as React, Vue, or Angular.

Use of requestAnimationFrame

For animations, use requestAnimationFrame instead of setTimeout or setInterval. requestAnimationFrame optimizes animation by synchronizing with the browser's refresh rate.

Example of requestAnimationFrame

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Debouncing and Throttling

To handle events that fire frequently, like scroll or resize, use debouncing and throttling techniques.

Example of Debouncing

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Example of Throttling

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Conclusion

Applying best practices and optimization techniques when manipulating the DOM is crucial to maintaining high performance and offering a smooth user experience. From minimizing reflows and repaints to using advanced techniques like requestAnimationFrame, debouncing, and throttling, these strategies help us improve the efficiency of our web applications. In the next chapter, we will explore various tools and libraries that can facilitate DOM manipulation.


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