JavaScript Problem

[robeng]

Hi! I have a javascript file that is beaing loaded last. In the file this code is executed:

var x = document.getElementById("bildfram1").offsetHeight;

document.getElementsByTagName("header").style.top = "calc(x/2)";

But I get this error in the console: Uncaught TypeError: Cannot set property 'top' of undefined

Any help on how to fix this!

Thanks in advance!

[Mooshe]

document.getElementsByTagName() does not return an HTMLElement, but rather an array of elements. You would need to iterate through the list to modify the style of each element:

 

for(h in document.getElementsByTagName("header")) {
  h.style.top = ...;
}

if you just want to edit one specific element, I would recommend providing an ID attribute to that element to select it.