windowgetComputedStyleelement

The `window.getComputedStyle()` method in JavaScript is used to retrieve the final, computed values of all CSS properties of an element. This means it returns the style values after all stylesheets (inline styles, internal stylesheets, external stylesheets, and browser defaults) have been applied and any cascading or inheritance rules have been resolved.

To use `window.getComputedStyle()`, you pass the element whose styles you want to inspect as an argument. The method returns a live `CSSStyleDeclaration` object, which is a collection of all computed CSS properties for that element. You can then access individual property values by their names, for example, `element.style.color` or `element.style.getPropertyValue('background-color')`.

It's important to note that `getComputedStyle()` returns the *computed* value, which might differ from the value set in a stylesheet. For instance, if a stylesheet sets `color: red;` and an inline style sets `color: blue;`, `getComputedStyle()` will return `blue`. If a relative value like `width: 50%` is used, `getComputedStyle()` will return the absolute pixel value.

The second optional argument to `getComputedStyle()` is a pseudo-element string, such as `::before` or `::after`. This allows you to inspect the computed styles of pseudo-elements associated with the target element. If no pseudo-element is specified, it defaults to null.