You can only select in a loop. What is the size of the number?

You should not use tr numbers as classes, because there are many classes bound to tr. You can completely bind numbers to data-num. The logic is probably as follows. Maybe some selectors are not written so accurately

html table:

<table id='example_table'>
    <thead>
        <th>1<th>
        <th>2<th>
        <th>3<th>
    </thead>
    <tbody>
        <tr data-num="1">
            <td>1<td>
            <td>2<td>
        </tr>
        <tr data-num="2">
            <td>1<td>
            <td>2<td>
        </tr>
        <tr data-num="3">
            <td>1<td>
            <td>2<td>
        </tr>
    </tbody>
</table>

js:

$('#example_table tr').on('click', function(e) {
    var select_tr_num = $this.data('num');
    var request_trs = [];
    $.each($('#example_table tr'), function(i, obj) {
        if (!obj.data('num') > select_tr_num) {
            select_tr_num.push(obj);
        }
    });
    console.log(request_trs );
}); 

What the first floor said is right. Generally, no one names a class with a number. They usually add a custom attribute

Traverse the values ​​of all classes and then compare and store them. (ps: But using numbers as classes is not very standard.)

Sort by class, and then get all the tr before the target tr