这样写 火狐浏览器不支持？

Question

var mousewheelevt=(/Firefox/i.test(navigator.userAgent))?"DOMMouseScroll": "mousewheel"//FF doesn't recognize mousewheel as of FF3.x

      if(document.attachEvent) //if IE (and Opera depending on user setting)
      {document.attachEvent("on"+mousewheelevt,this.menu)
      console.log(21121)
      }
      else if(document.addEventListener) //WC3 browsers
      {
          document.addEventListener(mousewheelevt, this.menu, false)
          console.log(21111121)
      }

Answer 1

DOMMouseScroll 是FF支持的独有滚轮事件，mouseWheel是以前IE和使用webkit内核浏览器支持的滚轮事件，现在的最新的现代浏览器支持wheel事件。
下面是MDN提供的滚轮事件跨浏览器兼容处理：

(function(window,document) {

    var prefix = "", _addEventListener, support;

    // detect event model
    if ( window.addEventListener ) {
        _addEventListener = "addEventListener";
    } else {
        _addEventListener = "attachEvent";
        prefix = "on";
    }

    // detect available wheel event
    support = "onwheel" in document.createElement("div") ? "wheel" : // Modern browsers support "wheel"
              document.onmousewheel !== undefined ? "mousewheel" : // Webkit and IE support at least "mousewheel"
              "DOMMouseScroll"; // let's assume that remaining browsers are older Firefox

    window.addWheelListener = function( elem, callback, useCapture ) {
        _addWheelListener( elem, support, callback, useCapture );

        // handle MozMousePixelScroll in older Firefox
        if( support == "DOMMouseScroll" ) {
            _addWheelListener( elem, "MozMousePixelScroll", callback, useCapture );
        }
    };

    function _addWheelListener( elem, eventName, callback, useCapture ) {
        elem[ _addEventListener ]( prefix + eventName, support == "wheel" ? callback : function( originalEvent ) {
            !originalEvent && ( originalEvent = window.event );

            // create a normalized event object
            var event = {
                // keep a ref to the original event object
                originalEvent: originalEvent,
                target: originalEvent.target || originalEvent.srcElement,
                type: "wheel",
                deltaMode: originalEvent.type == "MozMousePixelScroll" ? 0 : 1,
                deltaX: 0,
                deltaY: 0,
                deltaZ: 0,
                preventDefault: function() {
                    originalEvent.preventDefault ?
                        originalEvent.preventDefault() :
                        originalEvent.returnValue = false;
                }
            };
            
            // calculate deltaY (and deltaX) according to the event
            if ( support == "mousewheel" ) {
                event.deltaY = - 1/40 * originalEvent.wheelDelta;
                // Webkit also support wheelDeltaX
                originalEvent.wheelDeltaX && ( event.deltaX = - 1/40 * originalEvent.wheelDeltaX );
            } else {
                event.deltaY = originalEvent.deltaY || originalEvent.detail;
            }

            // it's time to fire the callback
            return callback( event );

        }, useCapture || false );
    }

})(window,document);

Answer 2

怎么觉得这么复杂呢