How to target tag a inside div with this?

Question

<c:forEach items="${list}" var="item">
    <div class="block" id="${item.id}" data-num="${item.itemRead}">
        <a id="${item.id}"
            href="javascript:showFeedItem('${item.id}','${item.itemRead}');">
    </div>
</c:forEach>

Why do I have undefinded attribute name data-num when creating a new data attribute data-num ? jQuery:

     $(document).ready(function(){
            $('.block').each(function(i, obj) {
                if($(this).attr("data-num")=="0"){
                   //need to style a inside this
                    $(this).css("background-color","black");
                }
            });
        });

How to target a like this:

 $('.block[id="' + id + '"] a').css('color', 'black');

but using $(this).css("background-color","black"); ?

Answer 1

Pass this as the context to jQuery selector

$(document).ready(function () {
    $('.block').each(function (i, obj) {
        if ($(this).attr("data-num") == "0") {
            //need to style a inside this
            $('a', this).css("background-color", "black");
            //or $(this).find('a').css("background-color", "black");
        }
    });
});

You can also shorten this to

$(document).ready(function () {
    $('.block[data-num="0"] a').css("background-color", "black");
});

Answer 2

如果要获取this代码的直接后代（如代码中的代码），则可以使用.children（）方法。

$(this).children(a).css("background-color","black");

Answer 3

I guess you need to change this:

<c:forEach items="${list}" var="item">
    <div class="block" id="${item.id}" data-num="${item.itemRead}">
        <a href="javascript:showFeedItem('${item.id}','${item.itemRead}');">
    </div>
</c:forEach>

removed id="${item.id}" from the anchor. What seemed to me that you are adding same ids to different items in a single page but it has to be unique for each element.

Now in the js you have to use .find() to style the anchor and style it:

$(document).ready(function(){
    $('.block').each(function(i, obj) {
        if($(this).attr("data-num")=="0"){ // or if($(this).data("num")=="0"){
            $(this).find('a').css("background","black");
        }
    });
});