CSS Animations + Javascript = Hell

frob.js

// This is a snippet that may or may not eventually make it live to my wobsite.
// This is the shortest code I currently know how to write that triggers my
// in/out animations correctly on toggle - every time - in the browser.
// The "Every Time" bit is the hardest bit.

function toggleReq() {
  requirementsOpen = !requirementsOpen;
  if(requirementsOpen) {
    req.style.height=document.getElementById("reqcontent").offsetHeight+8+"px";
    
    //prevents animations from stepping on each others' toes.
    if(sync !== null) { window.clearTimeout(sync); }
    
    //Timeout required, because otherwise the browser will do Odd Things
    //like flash a 0px tall height, or animate in from the wrong height.
    sync = window.setTimeout(function() {
      //frob whether or not we even want animations, because of the above
      //"Browser will do bad things otherwise" reason.
      req.classList.toggle("anim", true);
      //finally make it small.
      req.style.height="1em";
      
      //==================
      //CSS ANIMATIONS WHY
      //==================
      //Apparently all of this toggling is ENTIRELY NECESSARY,
      //without which the animation will Not Always Start(tm)
      document.getElementById("plus").classList.toggle("spinOut", true);
      document.getElementById("hbar").classList.toggle("minus", true);
      document.getElementById("hbar").classList.toggle("minus", false);
      document.getElementById("plus").classList.toggle("spinIn", false);
      sync = null;
    }, 50);
  } else {
    //prevent toe-stepping-on
    if(sync !== null) { window.clearTimeout(sync); }
    
    //turn on animations
    req.classList.toggle("anim", true);
    
    //prep the spin animation
    document.getElementById("plus").classList.toggle("spinOut", false);
    document.getElementById("hbar").classList.toggle("minus", false);
    
    //do the spin animation in a timeout, otherwise it (apparently) will
    //not always frob correctly.
    sync = window.setTimeout(function() {
      document.getElementById("hbar").classList.toggle("minus", true);
      document.getElementById("plus").classList.toggle("spinIn", true);
      //In order to make the browser animate opening the div to the full
      //content height, we must SPECIFY the full content height. Stating "auto"
      //instead will cause the browser to animate the div to 0px and then suddenly
      //snap to full height for who-knows-what-reason.
      req.style.height=document.getElementById("reqcontent").offsetHeight+8+"px";
      
      //in order to let the text reflow when the browser window is resized, we actually
      //*DO* want the req-div's style to say height:auto. Unfortunately, as stated above,
      //if we set it to auto it will animate like it has Palsy.
      //The solution is yet ANOTHER setTimeout.
      //
      // "Let's Nest Even More Callbacks!" (dot-tumblr-dot-com)
      sync = window.setTimeout(function() {
        req.classList.toggle("anim", false);
        req.style.height="auto";
        sync = null;
      }, 500);
    }, 50);
  }
}

also, Is This Literate Programming? (yes)