help with javascript to css to twine

StoryInit passage
<<set $myFont=["20px", "40px", "60px", "80px"]>>

<style>

  <button class="content">Fight</button>
  <button class="content">Bag</button>
  <button class="content">Pokemon</button>
  <button class="content">Run</button>

</style>

<<set $elements = document.getElementsByClassName("content")>>
<<for _x = 0; _x < $elements.length; _x++>>

<<set $elements[_x].style.fontSize=$myFont[_x]>>


<</for>>

Removing the style shows the buttons all the same size, while adding it gives an "undefined function" error.

How do I get this array to loop through the Class CSS and change each ones font size accordingly? Put it in the passageheader or before the passage loads its DOMS? or whatevers?