Why Does `Element.style` Return Different Values for Inline and Master Stylesheet Styles?

Display Style Retrieval Discrepancy in Master Stylesheets

When accessing an element's style through JavaScript's Element.style property, it's important to note potential differences in behavior based on how the style is declared.

In the scenario described, an initial display:none style was set inline on a DIV element. However, the element was then hidden when the initial style was moved to a master stylesheet. Interestingly, accessing the element's style.display property returned an empty string, while the same property accessed via an inline style returned "none."

This behavior is attributed to the distinction between declared style and computed style. Declared styles are those explicitly assigned to an element, either inline or through a stylesheet. Computed styles, on the other hand, represent the final rendered style of an element, taking into account all relevant factors, including inherited and cascaded styles.

When accessing Element.style, you are only getting the declared style. To obtain the computed style, which reflects the actual style applied to the element, you must use the window.getComputedStyle() method. This method provides a comprehensive representation of the element's styling, including properties affected by inheritance, cascading, and browser default values.

By using getComputedStyle(), you can reliably retrieve the display style of an element, even when it is initially hidden through a master stylesheet:

const element = document.getElementById('myDiv');
const display = getComputedStyle(element).getPropertyValue('display');
// display will now return 'none' or 'block', as appropriate

This corrected approach ensures that you access the accurate computed style of the element, regardless of how its style is declared.

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