How to read inline styling of an element?

Question

I'd like to know if it's possible to determine what inline styling has been attributed to an HTML element. I do not need to retrieve the value, but rather just detect if it's been set inline or not.

For instance, if the HTML were:

<div id="foo" style="width: 100px; height: 100px; background: green;"></div>

How can I determine that width, height, and background have been explicitly declared, inline?

As far as I can tell, the solution can work two ways. I can ask it if a specific attribute is set and it will tell me true or false, or it can tell me all attributes that have been set. Like so:

var obj = document.getElementById('foo');
obj.hasInlineStyle('width');  //returns true;
obj.hasInlineStyle('border'); //returns false;

//or

obj.getInlineStyles();   //returns array with values:
                       // 'width' 'height' and 'background'

I'm not interested in css attributes that are inherited via declarations in a stylesheet, only inline styles. One last thing, I have no control over the HTML source.

Thanks

Answer 1

Updated to work with IE

You could try something like this

function hasInlineStyle(obj, style) {
    var attrs = obj.getAttribute('style');
    if(attrs === null) return false;
    if(typeof attrs == 'object') attrs = attrs.cssText;
    var styles = attrs.split(';');
    for(var x = 0; x < styles.length; x++) {
        var attr = styles[x].split(':')[0].replace(/^\s+|\s+$/g,"").toLowerCase();
        if(attr == style) {
            return true;
        }
    }
    return false;
}

So if you have an element like this:

<span id='foo' style='color: #000; line-height:20px;'></span>

That also has a stylesheet like this:

#foo { background-color: #fff; }

The function would return...

var foo = document.getElementById('foo');
alert(hasInlineStyle(foo,'color')); // true
alert(hasInlineStyle(foo,'background-color')); // false

Answer 2

The style property of an HTML Element returns a style object which lists all the properties. Any that have a value (other than null or empty string) have been set on the inline style attribute.

Answer 3

You may want to try doing something like:

var obj = document.getElementById("foo");
var obj_has_background = (obj.style.background != "");
var obj_has_width = (obj.style.width != "");
var obj_has_height = (obj.style.height != "");

Seems a bit long, but this is the best (and shortest) solution I could come up with.

Answer 4

Are you trying to check if a certain styling attribute exists, or just want a list of the possible attributes? If you already know the attribute, then you can just use

hasStyle(obj,'width');
function hasStyle(obj, style)
{
     switch(style)
         case 'width':
              return obj.style.width ? true : false;
         case 'background':
              return obj.style.background ? true : false;
}

You can use Paolo's function to generate an array of the styles.