Another option is to use the getBoundingClientRect function. Please note that getBoundingClientRect will return an empty rect if the element's display is 'none'.
Example:
var elem = document.getElementById("myDiv"); if(elem) { var rect = elem.getBoundingClientRect(); console.log("height: " + rect.height); } UPDATE: Here is the same code written in 2020:
const elem = document.querySelector("#myDiv"); if(elem) { const rect = elem.getBoundingClientRect(); console.log(`height: ${rect.height}`); }