Best Practices for DOM Manipulation Using JavaScript
Jul 11, 2025 am 03:10 AM
When operating the DOM, you should reduce the number of accesses, use modern APIs, avoid memory leaks, and combine asynchronous throttling and anti-shake. 1. Avoid frequent operation of DOM in loops. It is recommended to build strings first or use DocumentFragment to batch processing; 2. Use querySelector and querySelectorAll to improve code readability and flexibility; 3. Clean event listeners before removing elements to prevent memory leaks; 4. Use requestAnimationFrame or debounce/throttle to control the execution frequency for high-frequency events.
Direct manipulation of DOM is one of the core features of JavaScript, but if you don't pay attention to the methods, it can easily affect performance or lead to difficult-to-maintain code. Mastering some best practices can make your operations more efficient and reliable.
1. Reduce the number of DOM operations
Frequent access and modification of DOM is the enemy of performance. Each change to the DOM can trigger the browser's reflow and repaint, especially when operating the DOM in a loop, the performance loss will be very obvious.
- Avoid direct manipulation of DOM in loops:
// Not recommended for (let i = 0; i < items.length; i ) { document.getElementById('list').innerHTML = '<li>' items[i] '</li>'; }
// Recommended: first build the string and then insert let html = ''; for (let i = 0; i < items.length; i ) { html = '
- Using document fragments (DocumentFragment) to batch operate nodes can also effectively reduce the number of reorders. ### 2. **Use modern APIs to improve readability and efficiency** Modern APIs such as `querySelector` and `querySelectorAll` are more flexible and semantic than old-fashioned `document.getElementById` and `document.getElementsByTagName`. - Example: ```javascript const container = document.querySelector('#container'); const buttons = document.querySelectorAll('.btn');
- These methods support CSS selector syntax and can write more concise and easy-to-understand selection logic.
- Note:
querySelectorAllreturns a static NodeList, which will not be updated dynamically likegetElementsByClassName.
3. Avoid memory leaks
Improper DOM operation can cause memory leaks, especially in event listening and data binding.
Frequently asked questions include:
- Added a listener to the DOM element, but it was not manually unbinded when removing the element;
- The DOM element is referenced in the closure, which cannot be garbage collected.
Suggested practices:
- Before removing elements, use
removeEventListenerto clean the listener; - Automatically manage life cycles using WeakMap or modern framework data binding mechanisms;
- If you use jQuery and other libraries, make sure to call its cleaning method (such as
.off());
4. Use asynchronous operation with throttling and anti-shake
Some DOM operations respond to user behavior, such as window adjustment, scrolling, etc. If these operations are performed too frequently, they will affect performance.
Solution:
- Use
requestAnimationFrameto optimize animation or render-related operations; - Use throttle or debounce functions to control the execution frequency for high-frequency events;
Example: Add anti-shake treatment to window resize
function debounce(func, delay) {
let timer;
return function() {
clearTimeout(timer);
timer = setTimeout(() => func.apply(this, arguments), delay);
};
}
window.addEventListener('resize', debounce(() => {
console.log('Resize handled');
}, 200));Basically that's it. DOM operation may seem simple, but errors are prone to details. Only by making rational use of modern APIs, controlling operation frequency, and paying attention to resource release can we write fast and stable code.
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