jquery取对象数组元素的错误方式

1 <div id="div1">
2     <span>a</span>
3     <span>b</span>
4     <span>c</span>
5 </div>

1 $(function() {
2     var div_span = $("#div1 span");
3     for( var i = 0; i < div_span.length; i++ ) {
4         div_span.[i].html(i);
5     }
6 });

1 for( var i = 0; i < div_span.length; i++ ) {
2     div_span.eq(i).html(i);
3 }

1 $(function() {
2     var div_span = $("#div1 span");
3     var i = 0;
4     div_span.each( function(){
5         $(this).html(i);
6         i++;
7     });
8 });