make unique ids

HTML

<span id="my-id">Lorem</span>
<span id="my-id">ipsum</span>
<span id="my-id">dolor</span>
<span id="my-id">sit</span>
<span id="my-id">amet</span>
<span id="my-id">amet</span><span id="my-id">amet</span><span id="my-id">amet</span>
<span id="my-id">sdds</span>
<span id="my-id">amet</span>
<span id="my-id">amet</span>
<span id="my-id">amet</span>
<span id="my-id">amet</span>

CSS

.cls{
    border:1px solid orange;
}

JavaScript

//make the id's unique
$('span[id=my-id]').each(function(i,el){
    el.id=el.id+'-'+i;
});

//select all spans with the id starting with 'my-id'
$('span[id^=my-id]').addClass('cls');