How to Correctly Modify HTML Element Styles Using JavaScript When Styles Are Defined Externally?

How to Modify Style for HTML Elements (Styled Externally with CSS) Using JS?

When attempting to alter the style of an HTML element using JavaScript, you may encounter issues. Here's a scenario where you aim to change the background color of a

element with the class "home" to green upon clicking that element. However, this doesn't work as expected. Let's examine the potential reasons for this issue.

The Original Code:

function selectHome() {
  console.log("test");
  document.getElementsByClassName("home").style += "background-color:green;";
}

Problem: Using getElementsByClassName and Mutating the style Property

The issue stems from the use of getElementsByClassName and the incorrect approach to modify the style. Here's a breakdown of the problems:

1. Using getElementsByClassName: getElementsByClassName returns a live node list, which means it updates dynamically as the DOM changes. However, here, you only need a reference to the first matching element, not an up-to-date list.
2. Mutating the style Property: Modifying the style property as a string (e.g., style = "background-color:green;") is not the recommended method. It's error-prone and can lead to unintended side effects.

Solution: querySelector and Setting CSS Properties

A better approach is to use querySelector to retrieve a reference to the required element and modify its CSS properties directly:

document.querySelector(".home").style.backgroundColor = "green";

Benefits of querySelector:

• Non-Live Node Return: querySelector returns a single node, not a live node list, which avoids potential performance issues.
• Consistency: It provides a more consistent and reliable way to select and modify elements.

Remember, when modifying the style of an element, it's best practice to set CSS properties directly instead of using string concatenation to alter the style property. This approach ensures clarity and simplifies future maintenance.

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