How to compel work scripts after loading page?

Question

"place scripts under </body>" - don't work
"place scripts after </body>" - don't work.

I'm tired :(

Help me, please.

I'm trying to do some animation and i need to find out width of my element through getComputedStyle, but it's don't work, because scripts loads before loading page. :( *crying*

var menuWidth = getComputedStyle(btnStart[0].style.width, '')

TypeError: failed to execute 'getComputedStyle' on 'window': parameter 1 is not of type 'element'

i close to understand it. *don't crying*

Answer 1

window.onload = function () {
// your code here
}