我应该如何引用document.getComputedStyle中的特定元素？

Question

I am making a game where there is a draggable object and I would like to store its actual place in real time. I was told I should use getComputedStyle but it only works in case I use

var computedStyle = getComputedStyle(document.body, null)

I mean if I add

document.write(computedStyle.marginTop)

it works and it writes the value of the top margin. But I need a div element's place.. I tried using

    var place = document.getElementById("draggable");
    var computedStyle = getComputedStyle(place, null);
    document.write(computedStyle.marginTop);

but it does nothing. I also tried

var computedStyle = getComputedStyle(document.getElementById("draggable"), null);

but it also did not work.

Can somebody please help me out how should I refer to the div element with the id "draggable"?

Answer 1

The developer docs at https://developer.mozilla.org/en-US/docs/Web/API/Window.getComputedStyle seem to indicate that the following should succeed:

var elem1 = document.getElementById("elemId");
var style = window.getComputedStyle(elem1, null);

So, try adding window. to your getComputedStyle clause, and check that your div is named correctly.

If neither of those two things help, check your javascript console for errors.