Detect inline/block type of a DOM element

How to detect whether a DOM element is block or inline with javascript?

For example, is there a function/property which returns 'inline' for a '<a>' tag (or 'block' for a '<p>' tag)?

Thank you.

Answers:

Answer

You can go with getComputedStyle() and currentStyle to get the calculated styles for an element. This should do it:

function getDisplayType (element) {
    var cStyle = element.currentStyle || window.getComputedStyle(element, ""); 
    return cStyle.display;
}

To be a little clearer, computed styles contain values for every style property, even for those that don't have a style property set. Those values will be the default value so in the case of an unstyled <a> element, display will return inline:

function getElementDefaultDisplay(tag) {
    var cStyle,
        t = document.createElement(tag),
        gcs = "getComputedStyle" in window;

    document.body.appendChild(t);
    cStyle = (gcs ? window.getComputedStyle(t, "") : t.currentStyle).display; 
    document.body.removeChild(t);

    return cStyle;
}

Tested in latest Firefox, Chrome and IE7/IE8.

Results:

> getElementDefaultDisplay("a")
inline
> getElementDefaultDisplay("div")
block

Update: edited to give preference to standards compliance/getComputedStyle() in IE9, which supports both methods.

Answer

The traditional and rather ugly way of doing this is to consult a list of element names for block-level elements:

var blockRegex = /^(address|blockquote|body|center|dir|div|dl|fieldset|form|h[1-6]|hr|isindex|menu|noframes|noscript|ol|p|pre|table|ul|dd|dt|frameset|li|tbody|td|tfoot|th|thead|tr|html)$/i;

function isBlockLevel(el) {
    return blockRegex.test(el.nodeName);
}
Answer

Consider that a block element may have been added to the dom containing a class with display:none. In that case you would need to know the default for that element. The following code gets a default style setting for an element (http://jsfiddle.net/jameswestgate/qBV5c/embedded/):

function getDefaultStyle(nodeName, property) {
    var div = document.createElement('div');
    div.setAttribute('style','position:absolute; left:-9999px;');

    var el = document.createElement(nodeName);
    div.appendChild(el);
    document.body.appendChild(div);

    var result = getComputedStyle(el, null).getPropertyValue(property);
    document.body.removeChild(div); 

    return result;
}

In this case call it using the nodeName of eg p and the display property which should return block or inline

getDefaultStyle('p', 'display'); //returns block

(For IE browsers, you need to use currentStyle instead of getComputedStyle)

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