How to pass variable with jquery element class?

Question

JavaScript

For example, I want to change class 2 color to green
<div id="1" class="2">yo</div>
I find the class by id and put it in the "my" variable, I want the color to change on click

var my = $('#1').attr('class');
$(my).click(function() {
  $(my).css( "color", "green" )
});

But nothing happens. How to solve the problem?

Answer 1

The selector for classes starts with a dot:
$('.' + my)

Answer 2

Имена классов начинаются с точки:

var my = '.' + $('#1').attr('class');
$(my).click(function() {
  $(my).css( "color", "green" )
});