Function init

scripts/smoothScroll.js:220–262

* Sets up scrolls array, determines if frames are involved.

()

   * Sets up scrolls array, determines if frames are involved.
   */
  function init() {
    if (initDone || isExcluded || !document.body) {
      return;
    }
    initDone = true;
    let body = document.body;
    let html = document.documentElement;
    let windowHeight = window.innerHeight;
    let scrollHeight = body.scrollHeight;
    // check compat mode for root element
    root = document.compatMode.indexOf("CSS") >= 0 ? html : body;
    activeElement = body;
    // Checks if this script is running in a frame
    if (top != self) {
      isFrame = true;
    }
    // TODO: check if clearfix is still needed
    else if (
      scrollHeight > windowHeight &&
      body.clientHeight + 1 < body.scrollHeight &&
      html.clientHeight + 1 < html.scrollHeight
    ) {
      if (root.offsetHeight <= windowHeight) {
        let clearfix = document.createElement("div");
        clearfix.style.clear = "both";
        body.appendChild(clearfix);
      }
    }
    // disable fixed background
    if (!options.fixedBackground && !isExcluded) {
      body.style.backgroundAttachment = "scroll";
      html.style.backgroundAttachment = "scroll";
    }
    if (!isFrame) {
      addEvent("message", function (e) {
        if (e.data.SS == "SmoothScroll") {
          let wheelEvent = e.data;
          wheelEvent.target = getFrameByEvent(e);
          wheel(wheelEvent);
        }
      });
    }
  }
  function getFrameByEvent(event) {
    let iframes = document.getElementsByTagName("iframe");
    return [].filter.call(iframes, function (iframe) {