jQuery：在mousemove事件期间检测按下的鼠标按钮

您可以编写一些代码来跟踪鼠标左键的状态，并且使用一些函数可以预处理mousemove事件中的事件变量.

要跟踪LMB的状态，请将事件绑定到mousedown和mouseup的文档级，并判断e.which以设置或清除标志.

The pre-processing is done by the tweakMouseMoveEvent() function in my code. To support IE versions < 9, you have to check if mouse buttons were released outside the window and clear the flag if so. Then you can change the passed event variable. If e.which was originally 1 (no button or LMB) and the current state of the left button is not pressed, just set e.which to 0, and use that in the rest of your mousemove event to check for no buttons pressed.

在我的示例中，mousemove处理程序只需调用传递当前事件变量的tweak函数，然后输出e.which的值.

$(function() {
    var leftButtonDown = false;
    $(document).mousedown(function(e){
        // Left mouse button was pressed, set flag
        if(e.which === 1) leftButtonDown = true;
    });
    $(document).mouseup(function(e){
        // Left mouse button was released, clear flag
        if(e.which === 1) leftButtonDown = false;
    });

    function tweakMouseMoveEvent(e){
        // Check from jQuery UI for IE versions < 9
        if ($.browser.msie && !e.button && !(document.documentMode >= 9)) {
            leftButtonDown = false;
        }

        // If left button is not set, set which to 0
        // This indicates no buttons pressed
        if(e.which === 1 && !leftButtonDown) e.which = 0;
    }

    $(document).mousemove(function(e) {
        // Call the tweak function to check for LMB and set correct e.which
        tweakMouseMoveEvent(e);

        $('body').text('which: ' + e.which);
    });
});

Try a live demo here: http://jsfiddle.net/G5Xr2/