How to Accurately Retrieve the Display Property of a DOM Element in JavaScript?

Retrieving the Display Property of a DOM Element

The document outlines an HTML structure containing two elements with varying display properties and a JavaScript script interacting with them. The script attempts to retrieve the display property of each element, but encounters unanticipated results. Upon displaying the values using JavaScript's .style.* properties, it observes empty strings instead of the expected "none" and "block" values. This leads to a query into the correct method to retrieve the display property accurately.

The key insight lies in understanding the difference between the style attribute and the applied style. The .style.* properties in JavaScript directly map onto the style attribute, which is a dynamic property present in an HTML element's inline styles. However, the displayed style or applied style is often influenced by factors such as CSS rules, inheritance, and user preferences. To retrieve the applied style, one must utilize the getComputedStyle() method.

For instance, if one were to apply the following CSS rule:

<code class="css">a {
    display: inline;
}</code>

The .style.display property for an anchor element would still return "none" (the inline value), even though the element appears inline due to the CSS rule. This is because the .style.* properties only reflect the inline style attributes, not the applied style.

To retrieve the applied style, one must use the getComputedStyle() method, as it provides access to all computed and cascaded styles, including those defined by user preferences and the browser's style engine. Here's an example:

<code class="javascript">var a = (document.getElementById('a'));
var display = window.getComputedStyle(a).display;
alert(display); // Will output "inline"</code>

As a best practice, it is advisable to separate presentation from logic by toggling .className rather than directly modifying style properties. This approach promotes modularity, maintainability, and code reusability.

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