this.io = {};有什么作用？
“setPath:”是什么？

修改问题：

为什么不用window.io={};
我找不到WebSocketMain.swf文件
为什么放在jQuery.io下？

this.io = {
    version: '0.6.1',

    setPath: function(path){
        if (window.console && console.error) console.error('io.setPath will be removed. Please set the variable WEB_SOCKET_SWF_LOCATION pointing to WebSocketMain.swf');
        this.path = /\/$/.test(path) ? path : path + '/';
    WEB_SOCKET_SWF_LOCATION = path + 'lib/vendor/web-socket-js/WebSocketMain.swf';
    }
};

try {
    if ('jQuery' in this)
        jQuery.io = this.io;
} catch (e) {
    try {
        if ('django' in this && 'jQuery' in django)
            django.jQuery.io = this.io;
    } catch (e) {

    }
}

if (typeof window != 'undefined'){
    // WEB_SOCKET_SWF_LOCATION = (document.location.protocol == 'https:' ? 'https:' : 'http:') + '//cdn.socket.io/' + this.io.version + '/WebSocketMain.swf';
    if (typeof WEB_SOCKET_SWF_LOCATION === 'undefined')
        WEB_SOCKET_SWF_LOCATION = '/socket.io/lib/vendor/web-socket-js/WebSocketMain.swf';
}