How to detect if element has 'auto' height

Please try:

document.getElementById("ele_id").style.height

Also check the following plugin:

http://gregpettit.ca/2012/jquery-check-if-element-has-auto-widthheight/

Update:

Based on other answers and lot of online research I came up with a mix of everything in a single function. Check out the jsfiddle here: https://jsfiddle.net/oriadam/d01ap7r6/3/

// input a jQuery element
// return true for elements with auto height (90-100% is considered auto as well)
// return false for elements with fixed height
function is_height_auto($e) {
    var e = $e[0],
        // check fixed style:
        chk = function(value) {
            return /\d/.test(value) && !/^(100|9\d)\%/.test(value);
        };

    // start from the first, easiest, inline styles
    if (chk(e.style.height)) {
        // console.log('fixed for having style', e.style.height)
        return false;
    }

    // start from the first, easiest, inline styles
    var overflow = getComputedStyle(e)['overflow'];
    if (overflow == 'scroll' || overflow == 'auto' || (e.tagName == 'BODY' && overflow == 'visible')) {
        // console.log('auto for having overflow or is body', getComputedStyle(e)['overflow'], e.tagName);
        return true;
    }

    // deprecated chrome way - check each rule that applies to the element
    if (typeof getMatchedCSSRules == 'function') {
        var i, MatchedCSSRules = getMatchedCSSRules(e) || [];
        for (i = MatchedCSSRules.length; i; i--) {
            if (MatchedCSSRules[i - 1].style.height) {
                // console.log('found height at MatchedCSSRules[' + (i - 1) + ']: ', MatchedCSSRules[i - 1], ' All matches: ', MatchedCSSRules)
                return !chk(MatchedCSSRules[i - 1].style.height);
            }
        }
    }

    // append something, see if height was changed, remove the something
    var originalHeight = $e.height(),
        $ghost = jQuery('<b style="display:block;height:1px;width:1px;padding:0;margin:0;">').appendTo($e),
        newHeight = $e.height();
    $ghost.remove(); // cleanup
    // console.log('Using a ghost got ',newHeight > originalHeight,' originalHeight=' + originalHeight + ' newHeight=' + newHeight) 
    return newHeight > originalHeight;
} //is_height_auto()

** Ghost element method explained (Previous answer):**

Greg Pettit had a pretty good answer in his blog, here is the main idea:

What’s unique about having auto height? Well, the fact that it allows height to change dynamically, of course!

1. Clone the element
2. Put it in visibility:hidden and position:absolute
3. Remove it's content
4. See if height changed (it should be around 0 now).

5. Cleanup

   var isAutoHeight = function(element) { // make a staging area for all our work. $('body').append('');

   // assume false by default
   var autoHeight = false;
   
   // clone the div and move it; get its height
   var clone = element.clone();
   clone.appendTo('#stage');
   var initialHeight = clone.height();
   
   // destroy all the content and compare height
   clone.html('');
   var currentHeight = clone.height();
   if (currentHeight < initialHeight) {
       autoHeight = true;
   }
   
   // get that clone and its smelly duplicate ID out of the DOM!
   clone.remove();
   // do the same for the stage
   $('#stage').remove();
   
   return autoHeight;
   

   };

Starting by Oriadam answer I created following jQuery function:

/**
* Checks if the element has explicitly set height by CSS styles.
* E.g.:
* 
*      var $myElement = jQuery('.my-element');
*      if ($myElement.hasExplicitHeight()) {
*          //...
*      }
* 
* This function is needed as .height() or .css('height') return a value, even 
* if no height property was explicitly set using CSS. 
* 
* @returns {Boolean}
*/
jQuery.fn.hasExplicitHeight = function() {
    var $element = jQuery(this);
    var $clone = $element.clone();
    $clone.html('');
    $clone.css('visibility', 'hidden');
    $clone.css('position', 'absolute');
    $clone.insertAfter($element);
    var hasExplicitHeight = $element.css('height') === $clone.css('height');
    $clone.remove();
    return hasExplicitHeight;
};

It works fine under condition that it is called only after the document is ready:

jQuery(function() { 
    // this code is launched only after the document is ready
    jQuery('.my-element').hasExplicitHeight();
});

Ran into a bug using the method of clone->heightCheck->remove innerHTML->heightCompare. Where it does not register a change in height, even if the element has 100%/auto height.

Instead, this method appears to work:

let autoHeight = false;
// Set up stage area with 100% height/width
const stage = document.createElement('div');
      stage.setAttribute('style', "position: relative; height: 100%; width: 100%;");
// Add stage to body
document.body.appendChild(stage);
// Clone the element and append to stage
const clone = element.cloneNode(false);
stage.appendChild(clone);
// Get Initial Height
const initialHeight = clone.offsetHeight;
// Squish content
stage.setAttribute('style', "position: relative; height: 1px; width: 1px;");
// Get new height
const currentHeight = clone.offsetHeight;
// Get max height (if it exists)
const hasMaxHeight = getComputedStyle(clone)["maxHeight"];
// Compare
if (currentHeight < initialHeight && hasMaxHeight == 'none') {
  // Has 100% or auto height, and no maxHeight
} else if (hasMaxHeight !== 'none') {
  // Flexible, but has a maxHeight
} else {
  // Constrained by height size
}
// Remove elements
stage.remove();