闭包1

HTML

<button>0</button> 
<button>1</button> 
<button>2</button> 
<button>3</button>

CSS

button{
  background-color: '#333';
}

JavaScript

var button = document.getElementsByTagName("button");

var addEventListener = function(nodes){
    var i;

    for(i = 0; i < nodes.length; i++){
        nodes[i].onclick = function(e){
            console.log(i);
        }
    }
}

addEventListener(button);