jQuery index on each function

I am curious why I need this index

$(document).ready(function() {
        $(".divToggle").each(function(index){
            var buttonId = $(this)[0].attributes["id"].value.toString();
            var idParts = buttonId.split('_');
            var uniquePart = idParts[0] + "_" + idParts[1] + "_" + "divContentPanel";             
            $(this).click(function() {
                 $("#" + uniquePart).toggle("slow");
            });            
        });
    });

Why do I need the "[0]" in "var buttonId =开发者_C百科 $(this)[0]…" Without it, I get an attributes["id"] is null error..

Use this instead

var buttonId = this.id;

or jQuery way

var buttonId = $(this).attr("id");

with $(this) you are still in the jquery model where the correct way to get id is .attr("id")

writing $(this)[0] drops you back into the DOM model where its as you wrote.

$(this)[0]

Is doing 2 things -

1. Getting you the first element in the matched set, as you're looping round a set of results one by one the index is probably redundant in this case
2. Returning a 'normal' JavaScript DOM object rather than a jQuery wrapped object

Looking at your code I believe you could achieve the same result by doing this -

var buttonId = this.id;

$(".divToggle").each(function(index, element){
    var buttonId = element.id,
        idParts = buttonId.split('_'),
        uniquePart = idParts[0] + "_" + idParts[1] + "_" + "divContentPanel";

    $(element).click(function() {
         $("#" + uniquePart).toggle("slow");
    });            
});

try

 var buttonId = $(this).attr("id");

Technically you don't need it with a little modification of your code. What happens with jQuery selectors is they are simply a bunch of element references in an array. so instead of

<div id ="myelement"></div>

you get

[<div id ="myelement"></div>]

using $(this) puts this in an array and allows it to be used with jQuery functions. If you aren't using jQuery functions just use this. So your code would become

var buttonId = this.attributes["id"].value.toString();