//eg1
layer.confirm('纳尼？', {
btn: ['按钮一', '按钮二', '按钮三'] //可以无限个按钮
,btn3: function(index, layero){
//按钮【按钮三】的回调
}
}, function(index, layero){
//按钮【按钮一】的回调
}, function(index){
//按钮【按钮二】的回调
});