Question

Here’s my code (what I’m stuck on is after the jump)

<script language="JavaScript" type="text/javascript" src="http://code.jquery.com/jquery-1.7.1.min.js"></script>
<script type="text/javascript">
var countThisMany = 4; //how many data-id's I want to count per "section" of images
var finalString = "";  //blank var to be used later, must be defined here.
</script>

<img src="foo.jpg" data-id="id1" data-item="1" />    // just a bunch
<img src="foo.jpg" data-id="id2" data-item="2" />    // of images with
<img src="foo.jpg" data-id="id3" data-item="3" />    // data-* usage to
<img src="foo.jpg" data-id="id4" data-item="4" />    // store two bits
<img src="foo.jpg" data-id="id5" data-item="5" />    // of information
<img src="foo.jpg" data-id="id6" data-item="6" />    // that I'll need
<img src="foo.jpg" data-id="id7" data-item="7" />    // to extract
<img src="foo.jpg" data-id="id8" data-item="8" />    // later on below.

<img src="bar.jpg" data-id="id9" data-item="1" />    // another set of images
<img src="bar.jpg" data-id="id10" data-item="2" />
<img src="bar.jpg" data-id="id11" data-item="3" />
<img src="bar.jpg" data-id="id12" data-item="4" />
<img src="bar.jpg" data-id="id13" data-item="5" />
<img src="bar.jpg" data-id="id14" data-item="6" />
<img src="bar.jpg" data-id="id15" data-item="7" />
<img src="bar.jpg" data-id="id16" data-item="8" />

<script type="text/javascript">
var item_array = $("img").map(function() {
    return $(this).attr("data-item");
}).get();

//alert(item_array);
//returns "1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8"


var id_array = $("img").map(function() {
    return $(this).attr("data-id");
}).get();
//alert(id_array);
//returns "id1,id2,id3,id4,id5,id6,id7,id8,id9,id10,id11,id12,id13,id14,id15,id16"


for (i=0;i<countThisMany;i++){
finalString=finalString+id_array[i]+';';
}

//alert(finalString);
//returns "id1;id2;id3;id4" -- could be more or less if "countThisMany" is changed to something other than 4 

</script>

This entire code is self-contained so feel free to save it as an HTML and uncomment the alerts to see the results.

What I need, however, is a step further. I would like to only collect the data-id of the img tags whose data-item are less than or equal to the variable countThisMany

So the end result of finalString would be “id1;id2;id3;id4;id9;id10;id11;id12”. And if countThisMany was changed to 2, for instance, it would be “id1;id2;id9;id10”

I feel as though I am so close but I can’t figure out how to only gather the first 4 of the first set of 8 images, and the first 4 of the second set of 8 images. Again, the total amount of images and how many I would need to capture vary, hence the “countThisMany’ var.

This is my first post to the amazing stackoverflow community, so I’m excited! Thanks to all contributors ahead of time!

Answer 1

Use filter method

var item_array = $("img").filter(function() {
    return parseInt($(this).data("item")) <= countThisMany;
}).map(function() {
    return $(this).data('id');
}).get();