事件委托

    <ul id='list'>
      <li>1</li>
      <li><span style="background: red;float:right">9999999999999</span></li>
      <li>3</li>
      <li>4</li>
      <li>5</li>
      <li>6</li>
      <li>7</li>
      <li>8</li>
    </ul>

window.onload = function(){
    var ul = document.getElementById("list");
    ul.onclick = function(eve){
        var event = eve || window.event;
        var target = event.target || event.srcElement;
        while(target.nodeName.toLowerCase() != 'li'){
            if(target === ul){
                target = null;
                break;
            }
            target = target.parentNode;
        }

        if(target){
            alert(target.innerHTML);
        }
    };
};