Set max-height using javascript

To make the animation time match what is expected, I would use el.scrollHeight to find the required height of the element.

document.getElementById ( "yourelementid" ).style.maxHeight = "100px";

See maxHeight Property

maxHeight was introduced in Windows Internet Explorer 7

Usually style attribute names are translated into javascript property names by removing the hyphens and camelcase the name instead.

So background-color becomes backgroundColor, text-align becomes textAlign and max-height becomes maxHeight.

You can set an element el's maximum height to mHeight by:

el.style.maxHeight=mHeight;

Remember to use a valid value for mHeight.