当数据来自数据库时，如何从一组复选框中仅选择4个

Question

I want to show JavaScript alert when user trying to choose more than four values from the group of checkbox the checkbox names are in array

<div class="checkbox alert alert-primary">

    <p><input type="checkbox" id="calorieCheckbox" name="txt_tradesman[]" value="<?php echo $restrad['tradesman_id'] ?>" onClick="return KeepCount()"><?php echo $restrad['fullname'] ?> <p>    

</div>

Answer 1

Here's jQuery version:

$('[name="txt_tradesman[]"]:checked').length