Why Does `element.style` Return Empty When Styles Are Defined in an External CSS File?

Understanding Why element.style Returns Empty

In JavaScript, the element.style property typically returns the inline style attributes applied directly to an element in the HTML document. However, inline style is not the preferred approach for styling elements as it may lead to code inconsistency and maintainability issues.

However, the issue arises when you explicitly define styles in an external CSS file and then attempt to access those styles using element.style. In this case, element.style will always return an empty object, leaving you puzzled.

Inline vs. Computed Styles

To understand this behavior, it's crucial to grasp the distinction between inline and computed styles. Inline styles refer to the style attributes directly applied to an element in the HTML document, while computed styles represent the combination of all applicable styles from every applicable source, including the inline styles, CSS stylesheets, and user agent styles.

JavaScript's Inability to Read CSS Styles Directly

JavaScript, on its own, does not have the ability to read CSS styles directly. Instead, it relies on the browser's rendering engine, which calculates the computed styles based on the cascade rules of CSS.

Therefore, when you access element.style, you are only accessing the inline styles, which are absent in your case as you have provided styles in an external CSS file. To obtain the computed styles, which include both inline and external CSS styles, you need to use the window.getComputedStyle(element) function.

Solution: Using getComputedStyle

In your scenario, the getComputedStyle function will provide the desired result:

console.log(window.getComputedStyle(document.getElementById('test')).display);

This line of code will log the value of the display property as defined in your CSS file, even though element.style.display returns an empty string.

So, the key takeaway is that element.style is specific to inline styles, while window.getComputedStyle provides access to both inline and external CSS styles, which is what you need to accurately retrieve styling information.

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