I have experienced the same issue in a jQuery plugin that I'm modifying for my own use. Basically, you can see from documentation that the parameter passed into getComputedStyle must be of type Element. Your plugin is passing window, the global variable pointing to the browser window, which is of type Window (who would have guessed?) into the function call. Their code looks something like this, I'm guessing:
var x = window.getComputedStyle(e);
They're probably calling this from a generic function that didn't verify that e is actually an Element and not a Window.
In my case, I'm only trying to circumvent the jQuery width() method on elements and include the border width and padding width. (It was a true doozy to figure out why I had to do that.) I reviewed how jQuery determines if the element is a Window and handled it similarly. Ultimately, this is what I ended up doing in my use case:
function getWidth(e) {
if (e != null && e === e.window) {
return $(e).width();
}
const css = window.getComputedStyle(e[0]);
const width = parseInt(css.width);
const pLeft = parseInt(css.paddingLeft);
const pRight = parseInt(css.paddingRight);
const bLeft = parseInt(css.borderLeft);
const bRight = parseInt(css.borderRight);
return width + pLeft + pRight + bLeft + bRight;
}
