How do I detect the inherited background-color of an element using jQuery/JS?

Using jQuery (or just JavaScript), how do I detect the inherited background-color of an element?

For example:

<div style="background-color: red">
    <p id="target">I'd like to know that the background-color here is red</p>
</div>

However:

$('#target').css('background-color') == rgba(0,0,0,0)

and

$('#target').css('backgroundColor') == rgba(0,0,0,0)

I'm asking for a general solution. $('#target').parent().css('background-color') would work in this instance, but not all.

Solution 1:

This could be accomplished by using the parent() in a loop until you reach the body tag:

I've set up a quick jsfiddle site with a little demo based on your code.

Edit: Good catch fudgey. After doing some testing it appears that IE7 will return 'transparent' instead of the rgba(0,0,0,0) value. Here's an updated link which I tested in IE7, Chrome 7, and Firefox 3.6.1.2. Another caveat with this approach: Chrome/Firefox will return rgb(255,0,0); IE returned 'red'.

Solution 2:

You can make use of window.getComputedStyle() to get the inherited value.

Caveat: You must manually declare the inheritance in css or inline.

#target{
  background-color: inherit;
}

Working example:

let bgc = window.getComputedStyle($('#target')[0],null).getPropertyValue("background-color");
console.log(bgc);

#target{
  background-color: inherit;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div style="background-color: red">
    <p id="target">I'd like to know that the background-color here is red</p>
</div>

Solution 3:

#target has no background color to read because background-color is not inherited.

you could write some javascript that keeps climbing up the DOM tree to search for a background-color declaration until it finds one., but there's no guarantee that that will get you the background color of an element that actually contains your #target.

btw. the css() method gets computed styles, so its giving you the correct reading.

Solution 4:

Here's the answer for people who hate browser inconsistency.

As explained, you need to test if this element has a transparent background, then if it does, walk through the DOM until you find a parent with background-color set - but that means testing whatever string each browser chooses to return.

Firefox, IE and others return transparent, Chrome/safari/webkit browsers etc return rgba(0, 0, 0, 0)... and I personally don't trust that there won't be some other exception out there somewhere, now or in the future.

If you don't like the idea of trusting a string given to you by a browser (and you shouldn't), you don't have to: just test against the background-color of an empty element.

Here's a JSBIN example of it in action. (to test on old IE, remove 'edit' from URL)

Usage: Plonk this code somewhere (it works as a jQuery plugin)...

(function($) {
  // Get this browser's take on no fill
  // Must be appended else Chrome etc return 'initial'
  var $temp = $('<div style="background:none;display:none;"/>').appendTo('body');
  var transparent = $temp.css('backgroundColor');
  $temp.remove();

jQuery.fn.bkgcolor = function( fallback ) {
    function test( $elem ) {
        if ( $elem.css('backgroundColor') == transparent ) {
          return !$elem.is('body') ? test( $elem.parent() ) : fallback || transparent ;
        } else {
          return $elem.css('backgroundColor');
        }
    }
    return test( $(this) );
};

})(jQuery);

...then you can get the 'inherited' background colour of any element like this:

var backgroundColor = $('#someelement').bkgcolor();

Or if you want a fallback to be applied instead of 'transparent' if no background-color is set here or anywhere behind this element (e.g. for matching overlays), send as an argument:

var backgroundColor = $('#someelement').bkgcolor('#ffffff');