Get all id values from checked checkbox in table

<table id="tab" border='1' style='width:100%'>
        <tr ><td>'hi'</td><td><input type='checkbox' id='1'/></td></tr>
        <tr><td>'hi'</td><td><input type='checkbox' id='2' /></td></tr>
        <tr ><td>'hi'</td><td><input type='checkbox'id='3' /></td></tr>
        <tr ><td>'hi'</td><td><input type='checkbox'id='4' /></td></tr>
</table>

this is example code, i need to return list of if that are checked, so if i check all of them i get lit[1,2,3,4] if i select only fist 2 list[1,2] and so on. Please help me!