Propagation JQuery 阻止冒泡法

$('span').bind("click", funciton(event){ //event : 事件对象
    var txt = $('#msg').html()+"some spans have been actived
";
    $('#msg').html(txt);
    event.stopPropagation();   //停止事件冒泡
});

用event.preventDefault();来阻止默认行为 （比如点击提交表单，验证表单内容，不符合条件，要阻止提交（默认行为）。

$("#sub").bind("click", function(event){
    var username = $("#username").val(); //get the input value
    if(username == ""){
        $("#msg").html("Input can't be empty.
");  //提示信息
        event.preventDefault();   //阻止默认行为
    }
});

also the event.stopPropagation() and event.preventDefault() can be changed to return false;