5、语句注释

javascript代码中，应合理出现注释，标注代码的用意，增加代码的可读性，方便代码维护和修改。

反例

 function fixedHeader() {
  var self = this,
      $root = $(self.$el),
      $ctRoot = $root.find('#ct-root'),
      $ctHeader = $root.find('.scroll-header'),
      ctHeaderH = parseInt(window.getComputedStyle($ctHeader[0]).height),
      maxOpactiyH = parseInt(ctHeaderH * 2),
      opacity = 0;
  $ctRoot.on('scroll', function() {
    var $this = $(this),
        scrollcur = $this.scrollTop();
    if (scrollcur > 0) {
      $ctHeader.removeClass('hide');
      if(scrollcur < maxOpactiyH){
        opacity = scrollcur/maxOpactiyH;
      }if(scrollcur > maxOpactiyH){
        opacity = 1;
      }
      $ctHeader.css('opacity', opacity);
    }else{
      $ctHeader.addClass('hide');
      $ctHeader.css('opacity', 0);
    }
  });
}

正例

function fixedHeader() {
  var self = this,
      $root = $(self.$el),
      $ctRoot = $root.find('#ct-root'),
      $ctHeader = $root.find('.scroll-header'),
      ctHeaderH = parseInt(window.getComputedStyle($ctHeader[0]).height),//头部高度
      maxOpactiyH = parseInt(ctHeaderH * 2),//滚动区间设在头部高度1.5倍
      opacity = 0;
  $ctRoot.on('scroll', function() {
    var $this = $(this),
        scrollcur = $this.scrollTop();
    //将导航条定位到顶部
    if (scrollcur > 0) {
      $ctHeader.removeClass('hide');
      //滚动1.5倍自身高度内，透明度变化
      if(scrollcur < maxOpactiyH){
        opacity = scrollcur/maxOpactiyH;
      }if(scrollcur > maxOpactiyH){//规避卡顿造成的影响
        opacity = 1;
      }
      $ctHeader.css('opacity', opacity);
    }else{
      $ctHeader.addClass('hide');
      $ctHeader.css('opacity', 0);
    }
  });
}