Jquery 初始化混淆

代码确保调用init()函数。

它将 init 函数绑定到加载 DOM 或页面时触发的事件侦听器。

如果这些事件已经由 readyState 确定触发，那么它直接调用 init，否则它会每 30 毫秒检查一次 readyState。

        // Call init function when DOM is loaded
        if (document.addEventListener) {
          document.addEventListener('DOMContentLoaded', init, false);
        }
        // Immediately invoked function expression that calls init
        // function if doScroll method does not throw error.
        (function() {
          try {
            document.body.doScroll('up');
            return init();
          } catch(e) {}
          // Call init function if DOMContentLoaded event has already been
          // fired or if page is already loaded.
          if (/loaded|complete/.test(document.readyState)) return init();
          // arguments.callee is a reference to it's executing function
          // which is this immediately invoked function expression.
          // It will keep calling it every 30 milliseconds while init
          // has not been called yet.
          if (!init.done) setTimeout(arguments.callee, 30);
        })();

        // Call init function when window is loaded.
        // `load` event is fired after DOMContentReady, when
        // everything has loaded in the page.
        if (window.addEventListener) {
          window.addEventListener('load', init, false);
        // Same as above but for IE versions 8 or less
        } else if (window.attachEvent) {
          window.attachEvent('onload', init);
        }
        function init() {
            // If init has been called then immediately return.
            if (arguments.callee.done) return;
            // Set flag on itself to indicate that it init been called.
            arguments.callee.done = true;
            // do your thing
            //[...]
        }