Number of divs with same class using jquery

Question

How can I find the number of divs with a specific class name using jquery

like here I would like to get the result as 2 for class name "failedtest". and I also want to access them through the id of outer div (1285766787423container)

<div id="1285766787423container" class="container">
    <div class="row">
        <div class="cell1">
        </div>
        <div class="failedtest">
        </div>
    </div>
    <div style="display: none;" class="row">
        <div class="cell1">
        </div>
        <div class="failedtest">
        </div>
    </div>
    <div style="display: none;" class="row">
        <div class="cell1">
        </div>
        <div class="cell2">
        </div>
    </div>
    <div style="display: none;" class="row">
        <div class="cell1">
        </div>
        <div class="cell2">
        </div>
    </div>
</div>

    <div id="1285766787423container" class="container">
    <div class="row">
        <div class="cell1">
        </div>
        <div class="failedtest">
        </div>
    </div>
    <div style="display: none;" class="row">
        <div class="cell1">
        </div>
        <div class="failedtest">
        </div>
    </div>
    <div style="display: none;" class="row">
        <div class="cell1">
        </div>
        <div class="cell2">
        </div>
    </div>
    <div style="display: none;" class="row">
        <div class="cell1">
        </div>
        <div class="cell2">
        </div>
    </div>
</div>

Answer 1

Try

$("#1285766787423container div.failedtest").length;

Answer 2

var numberOfFailedDivs = $('#1285766787423container .failedtest').length;

or if you want only the div elements with this class:

var numberOfFailedDivs = $('#1285766787423container div.failedtest').length;

Answer 3

$("#1285766787423container div.failedtest").size();

Answer 4

$("#1285766787423container div.failedtest").size();