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Last updated on 2024年5月25日

How can you optimize your JavaScript code for efficient DOM manipulation?

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Optimizing your JavaScript code for efficient Document Object Model (DOM) manipulation is crucial for improving the performance of your web applications. The DOM is a programming interface for web documents that represents the page so that programs can change the document structure, style, and content. JavaScript manipulates the DOM to interact with the HTML and CSS of a page, but inefficient manipulation can lead to slow page rendering and a poor user experience. By following best practices, you can ensure that your JavaScript code interacts with the DOM in the most efficient way possible.

本文章的要点总结

Cache element references:

Storing references to DOM elements you need repeatedly avoids the performance hit from accessing the DOM multiple times. Use variables to keep these elements handy, and watch your web apps speed up.
Batch your updates:

When making multiple changes to the DOM, do it in one go using DocumentFragment or a string of HTML. This reduces costly reflows and repaints, leading to smoother and faster page interactions.

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Ashan Dimantha

Software Engineering Intern @Fortude…

1 Minimize Access

Every time you access the DOM, there's a performance cost. To optimize, minimize the number of times your code touches the DOM. Store references to DOM elements you need to work with more than once. Use variables to hold onto elements after the first access. This way, you avoid repeated queries to the DOM tree, which can be a slow operation, especially if done excessively within loops or complex functions. By reducing direct DOM access, you ensure that your JavaScript runs faster and more efficiently.

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Oleh Ferents

Founder & CTO at LNOKS | SaaS Software Development | Dedicated teams & End-to-end Development
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Accessing the DOM is one of the most expensive operations in terms of performance. To minimize DOM access, reduce the number of times you need to read or write to the DOM. Cache references to DOM elements by storing them in variables rather than repeatedly querying the DOM.

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Ashan Dimantha

Software Engineering Intern @Fortude | CS Undergrad | UI/UX Engineer | Digital Marketer | AIESECer ??
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To optimize JavaScript for efficient DOM manipulation, minimize direct access. Cache frequently accessed elements to avoid repeated queries. Batch DOM updates to reduce reflows and repaints. Use document fragments for off-DOM operations before appending. Prioritize modern methods like querySelector over older ones. These strategies enhance performance by reducing unnecessary DOM interactions.

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Lucas Gusm?o Izar

Software Engineer & Architect | Team Leader | Node.js | C# | Azure
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O DOM deve ser acessado e modificado apenas quando realmente for necessário. Ter essa consciência é importante! é possível diminuir o acesso excessivo e recorrente ao DOM cacheando os elementos em variáveis e as utilizando para manipula??o de dados, assim como a utiliza??o dos fragmentos de documento (documentFragment) para cria??o de estruturas em memória.

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2 Batch Changes

Making multiple changes to the DOM can be expensive. Instead of inserting or modifying nodes one by one, consider batching these changes. You can use document fragments or build a string of HTML when adding multiple elements. Then, append this string or fragment to the DOM all at once. This reduces the number of reflows and repaints, operations the browser performs when the page's layout or visual content changes, which are computationally intensive and can lead to sluggish performance.

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Oleh Ferents

Founder & CTO at LNOKS | SaaS Software Development | Dedicated teams & End-to-end Development
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Making multiple DOM updates individually can be inefficient. Instead, batch your changes to the DOM. This means making all your modifications at once or grouping them to minimize the number of reflows and repaints.

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3 Use Selectors

Efficiently selecting elements within the DOM is key to optimizing manipulation. Prefer class and ID selectors over more complex query patterns, as they are faster for browsers to process. When using querySelectorAll , remember that it returns a static NodeList. This means it won't reflect changes made to the DOM that affect the list. For dynamic content, consider getElementsByClassName or getElementsByTagName , which return live HTMLCollections that update automatically.

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Oleh Ferents

Founder & CTO at LNOKS | SaaS Software Development | Dedicated teams & End-to-end Development
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Leverage efficient DOM selectors to find elements quickly. Use methods like querySelector and querySelectorAll for CSS-style selectors, and prefer more specific selectors to reduce the search scope.

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Ashan Dimantha

Software Engineering Intern @Fortude | CS Undergrad | UI/UX Engineer | Digital Marketer | AIESECer ??
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Optimizing JavaScript for DOM manipulation involves smart selector usage. Prefer efficient selectors like getElementById, getElementsByClassName, or querySelector for targeted access. Minimize generic selectors like getElementsByTagName to avoid full DOM traversal. Cache repeated selections to prevent redundant DOM traversals. Prioritize querySelectorAll for its flexibility and performance. Use context-based querying to limit searches within specific DOM branches, reducing overhead. These selector strategies streamline DOM manipulation, boosting JavaScript efficiency.

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4 Event Delegation

Event delegation is a technique where you use a single event listener to manage all events of a particular type for child elements. Instead of adding an event listener to each element, you add one to a parent element. This not only reduces memory usage by having fewer listeners but also simplifies management of event listeners as elements are added or removed from the DOM. This is particularly useful for dynamically generated content where attaching an event listener to each new element would be inefficient.

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Oleh Ferents

Founder & CTO at LNOKS | SaaS Software Development | Dedicated teams & End-to-end Development
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Event delegation allows you to handle events more efficiently by attaching a single event listener to a parent element instead of multiple listeners to individual child elements. This is particularly useful when dealing with a large number of dynamically created elements.

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5 Avoid Layout Thrashing

Layout thrashing occurs when JavaScript repeatedly reads and writes to the DOM, forcing the browser to perform layout calculations multiple times before the page is repainted. To avoid this, separate your read and write operations. Batch all reads first and then perform all writes. This approach allows the browser to batch layout operations together, minimizing reflows and improving performance. Recognizing and preventing layout thrashing can significantly boost the responsiveness of your web application.

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Oleh Ferents

Founder & CTO at LNOKS | SaaS Software Development | Dedicated teams & End-to-end Development
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Layout thrashing occurs when multiple reads and writes to the DOM are interleaved, causing excessive reflows and repaints. To avoid this, group your reads and writes separately.

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6 Optimize CSS

The efficiency of DOM manipulation is also tied to CSS performance. Complex CSS selectors can slow down JavaScript's ability to access elements in the DOM. Simplify your CSS by using classes and IDs instead of attribute or descendant selectors whenever possible. Also, avoid inline styles through JavaScript as they can trigger reflows. Instead, toggle classes on elements, letting CSS handle the visual changes. This separation of concerns leads to cleaner code and better performance.

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Ashan Dimantha

Software Engineering Intern @Fortude | CS Undergrad | UI/UX Engineer | Digital Marketer | AIESECer ??
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To optimize JavaScript for DOM manipulation, cache frequently accessed elements, reducing queries. Batch DOM operations using DocumentFragment improves efficiency. Prioritize modern DOM APIs like querySelectorAll(). CSS optimization, like class toggling for style changes, reduces recalculations. Delegate event listeners to parent elements for better scalability. These strategies enhance performance and maintain clean code, ensuring efficient DOM manipulation.

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Oleh Ferents

Founder & CTO at LNOKS | SaaS Software Development | Dedicated teams & End-to-end Development
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Optimizing your CSS can significantly improve DOM manipulation performance. Efficient CSS rules reduce the browser's workload during reflows and repaints.

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How can you optimize your JavaScript code for efficient DOM manipulation?

1

2

3

4

5

6

7

1 Minimize Access

2 Batch Changes

3 Use Selectors

4 Event Delegation

5 Avoid Layout Thrashing

6 Optimize CSS

7 Here’s what else to consider

Software Development

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How can you optimize your JavaScript code for efficient DOM manipulation?

1

2

3

4

5

6

7

1 Minimize Access

2 Batch Changes

3 Use Selectors

4 Event Delegation

5 Avoid Layout Thrashing

6 Optimize CSS

7 Here’s what else to consider

Software Development

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