How Can I Efficiently Modify Styles of Externally Styled HTML Elements with JavaScript?

Modifying Style Properties of Externally Styled HTML Elements Using JavaScript

When customizing the appearance of HTML elements dynamically with JavaScript, it may be necessary to modify style properties that are initially defined in external CSS stylesheets. While it's possible to do so using the document.getElementsByClassName() method, it comes with drawbacks.

Disadvantages of Using getElementsByClassName()

• Returns live node lists: getElementsByClassName() produces a live node list that constantly updates its contents based on DOM mutations, which can be inefficient for accessing single elements or large lists of elements.
• Prone to unnecessary searching: Even when only interested in the first匹配元素, the method iterates through the整个DOM to find all matching elements, only to discard most of them.

A Better Alternative: querySelector()

To efficiently and reliably modify style properties of externally styled HTML elements, it's recommended to use the querySelector() method instead. querySelector() scans the DOM for the first element matching a specified selector and returns a reference to that element. If no matching element is found, it returns undefined.

Example Modification

To change the color of the

element with the class "home" to green when clicked, you can use the following code:

const homeElement = document.querySelector(".home");
homeElement.style.color = "green";

This code safely retrieves the first element with the "home" class and directly modifies its color style property without the need for a live node list.

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