Cross-browser (IE8-) getComputedStyle with Javascript?

Question

Since IE8 does not support getComputedStyle, we can only use currentStyle. However, it does not return the real \"computed\" value

Answer 1

This was too big for an edit, so it was made an answer but it doesn't provide a full answer to the question at hand.

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Gabriel's answer fails with a property like "backgroundColor" or "background-color" depending on the browser version because .getPropertyValue expects the CSS property name and el.currentStyle[prop] needs the camel-case version.

Here's a fixed version which always expects the camel-case version:

function getStyle(el, prop) {
    return (typeof getComputedStyle !== 'undefined' ?
        getComputedStyle(el, null) :
        el.currentStyle
    )[prop]; // avoid getPropertyValue altogether
}