多个元素绑定同一事件

var nodes = document.querySelectorAll('li');
var add_the_headers = function(nodes){
        var helper = function(i){
            return fucntion(e){
                alert(i)
            }
        }
    }
    var i;
    for(i = 0;i<nodes.length;i+=1){
        nodes[i].onclick = helper(i)
    }