Response title
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if($("#unsubscribe input[type=checkbox]").prop('checked') == false){
$('#checkboxAlert').show();
evt.preventDefault();
}
<form id="unsubscribe">
<input type="checkbox" id="group0001" name="group0001" value="on" class="check custom-class" required oninvalid="this.setCustomValidity('Please select at least one option to proceed')"><label for="subscription">Email Group 1 Communication</label>
<input type="checkbox" id="groupsAll" name="groupsAll" value="on" class="check custom-class" required><label for="subscription">All Communication</label>
[a-zA-Z][a-zA-Z][a-zA-Z][0-9][0-9][0-9]{6}
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